Similar Posts


This plugin displays a list of posts which are related or similar to the current post.

This is version download latest version. It is compatible with WordPress 1.5–2.6.2.

Ideally, similarity or relatedness would be based on a post’s meaning. Tagging systems try to add meaning after the fact but suffer from two deficiencies, one practical and the other theoretical. When a blog already has many posts it can be impractical to retrofit a tagging system by tagging every post by hand. ‘Automatic’ services, like Yahoo’s, tend to produce too many suggestions which need to be culled, again by hand.

The theoretical problem with tagging is that it tries to pin down a meaning for a post by categorising it under a small number of types, whether those types belong to a predetermined hierarchy or arise by ‘folk’ classification. In fact, a post has a variety of meanings, a multitude of ways it can be related to other posts. Meaning doesn’t just lie in the intention of the author or in the classification of the reader; meaning also inhabits the text itself. Meaning is in the words.

The Similar Posts plugin compares posts by comparing their words. MySQL has a sophisticated full-text searching facility with a carefully tuned algorithm for judging the similarity between texts. Similar Posts extracts representative words from a post’s content, title, and tags and uses the full-text index to find the best matches between posts. This simple approach gives surprisingly good results.

The results can be tweaked in several ways to tailor them for you blog. By default the plugin chooses the 20 most frequent words to make its matches but the number is adjustable. It is worth experimenting to see how many words gives the best results for your blog — it has hardly any impact on speed, even if you set the value high enough to include the whole post. The relative importance given to words in your title may be adjusted so that well-chosen titles can be used to advantage or titles with little relevance downplayed. Similarly, tags can be used to improve matching or not according to your blog and it’s needs.

It is also possible to override the automatic similarity ranking by using a custom field. In the post edit screen create a custom field called ‘sp_similar’ with the ID value of the post to which you wish to ‘link’. You can link to multiple posts by entering a comma-delimited list of IDs.

The plugin has a settings page which lets you change how the output is generated and displayed. There is also a management page where you can change settings which affect the index.

Note: Similar Posts needs to know the ID of the post for which it is generating related posts. WordPress keeps track of that information in a global variable but unfortunately some other plugins can corrupt the data before Similar Posts gets a chance to use it. Similar Posts tries various tricks to get round this but sometimes it fails. The usual symptom is a list of similar posts that stays the same from page to page. You can help Similar Posts out by marking the current post manually by adding a line to your theme files. Find the place where the_content(); is used to display the current post and right after it put similar_posts_mark_current();.

Installation Instructions

  1. If upgrading from a previous version, first deactivate the plugin via the Plugins page and delete the plugin folder from your server.
  2. If you have been using the Similar Posts Feed plugin you should deactivate it as it is now obsolete.
  3. Upload the plugin folder to your /wp-content/plugins/ directory. You will also need to install the Post-Plugin Library.
  4. Go to your admin Plugins page and activate Similar Posts. This will automatically add a new table to enable fast, flexible full-text matching. If the plugin reports that there was a problem creating the table first try deactivating and reactivating the plugin.
  5. Put <?php similar_posts(); ?> at the place in your theme files where you want the list of similar posts to appear. Lorelle on WordPress has a good guide to modifying themes for plugins.

    If you are averse to editing template files you can also place the post listing automatically either as a widget in the sidebar of your widget-aware theme or after each post (from the plugin’s Placement submenu).

  6. Use the admin Settings|Similar Posts pages to set all the available options. Alternatively, the options can be overridden by passing a parameter to the similar_posts template tag.

Usage and Options

The configuration page will help you to set up the plugin to your satisfaction.

The Index Management Page

Using this settings subpage you can re-index your blog. There are two main settings which affect the indexing.

PHP is, by default, not very good at handling text that isn’t in English and you might find Similar Posts mangles extended characters. If so, you can get the plugin to use PHP multi-byte string library if it is available.

The second setting attempts to handle words with related meanings. For example, ‘animal’ and ‘animals’ should probably not count as two distinct words, nor ‘follow’, ‘follows’, ‘following’, etc. You can choose to build the index using a stemming algorithm that groups such words as one (if there is one available for your language) or you can try the fuzzy matching algorithm. Whether it is better to be strict or to be relaxed will depend on your website.

A third setting is for blogs written mainly in Chinese, Korean, or Japanese. The MySQL fulltext index used by Similar Posts has problems with these languages but this setting tries several ways to work around the issues. The setting currently only works when posts are encoded as UTF-8. I would be very glad to get opinions from users familiar with these languages.

To avoid excessive memory use the indexing routine processes posts in batches of 100. This figure can be reduced to shrink the memory consumption even further.

Language Issues

The underlying MySQL full-text indexing is obviously very locale-dependent — how words are divided or punctuation handled, what words are treated as noise, etc. all vary from language to language. For the Similar Posts plugin to work well the version of MySQL on your server must be properly setup in the appropriate language.

Similar Posts generates the terms it matches on by analysing the word frequency of a post while ignoring the most common ‘noise’ words — in English, words like ‘of’, ‘and’, ‘across’, ‘someone’, etc. It uses a so-called ‘stop list’ of common English words to ignore. In fact it uses the stop list a standard English installation of MySQL uses. Obviously this list will be useless for other languages so Similar Posts makes the stop list pluggable.

The Similar_Posts folder contains a subfolder, ‘languages’, with stop lists and stemmers for a German, English, French, Spanish, and Italian. The plugin checks the WPLANG constant (defined in wp-config.php) to see which language WordPress is using and looks for a file on that basis. If WPLANG is undefined or the appropriate file cannot be found the default English list is used.

If you are looking for help setting up a stop list in a language other than English a good resource can be found at Stemmers in PHP are harder to come by. You can work out how to adapt any you find by inspecting the provided stemming files.


I look forward to your help in ironing out any issues and implementing any good ideas. The plugin settings page has an option to submit bug reports but general comments can be left below.

Frequently Asked Questions

[faq list Similar Posts]
[faq list General Post Plugins]

415 Comments Add your own

  • 1. Rob  |  March 6th, 2008 at 10:07 pm

    Sukarto: I hope so! Try adding several different ‘real’ posts (i.e., with plenty of real words) and I hope that proper matching behaviour will follow. If it doesn’t we will have to work out what the strange difficulty is.

  • 2. Tanguillo  |  March 18th, 2008 at 6:40 pm

    Ok, when I activate the plugin, in wordpress 2.5 rc1 it shows me this weird, weird error, after says can not activate the plugin:

    Fatal error: Cannot redeclare similar_posts() (previously declared in /home/tangosco/public_html/wp-content/plugins/similar-posts/similar-posts.php:33) in /home/tangosco/public_html/wp-content/plugins/similar-posts/similar-posts.php on line 33

    More weird is that the plugin is actually activated, and the both menu options are working (And I have to tell you it look great)… But in my post it seems it doesn’t find any similar article.
    Let me know what other info I can give you to solve this.

  • 3. Rob  |  March 18th, 2008 at 9:06 pm

    Tanguillo That is certainly weird! Can you tell me if the wp_similar_posts database table has been created?

    If it has try using the Manage Similar Posts menu to reindex and see if that helps…

    Oh and did you deactivate and remove the old version before upgrading?

    Let me know…

  • 4. Tanguillo  |  March 18th, 2008 at 9:17 pm

    Well, that works!!!
    I mean, it still give me that error if I deactivate it/activate it, but after the reindex, my post show the similars post, and it seems very good.

    The only think that I did wrong the first time wast to try to activate it without copy the post-plugin-library folder first. It give an error, of course. Could be that the problem? Or maybe is a problem with the 2.5 version?

  • 5. Rob  |  March 18th, 2008 at 9:36 pm

    Tanguillo: I guess the activation ended strangely and left WP in a halfway state where the database table was installed but not indexed. I don’t know how to solve the activation issue apart from suggesting you deactivate and completely remove the plugin folders, check the plugin page is working and then reupload and reactivate. I have occasionally had similar tangles with other plugins if I tried renaming a folder while the plugin was activated.

    Let me know of any other problems.

  • 6. Rob  |  March 22nd, 2008 at 10:03 am

    Version 2.5 b4 fixes a problem with empty posts.

  • 7. Josette  |  March 22nd, 2008 at 5:53 pm

    Hi! I’ve just tried to install this Similar post plugin. When I want to activate it, it couldn’t be activated at all because it triggered a fatal error!

    This message appeared:

    Warning: require_once(/home2/childcec/public_html/bookslm//wp-content/plugins/post-plugin-library/output_tags.php) [function.require-once]: failed to open stream: No such file or directory in /home2/childcec/public_html/bookslm/wp-content/plugins/similar-posts/similar-posts.php on line 45

    Fatal error: require_once() [function.require]: Failed opening required ‘/home2/childcec/public_html/bookslm//wp-content/plugins/post-plugin-library/output_tags.php’ (include_path=’.:/usr/lib/php:/usr/local/lib/php’) in /home2/childcec/public_html/bookslm/wp-content/plugins/similar-posts/similar-posts.php on line 45

    I really like this plugin and hope I can continue using it! Thank you.

  • 8. Rob  |  March 22nd, 2008 at 6:23 pm

    Josette: Did you upload the post-plugin-library folder as well as the similar-posts folder?

  • 9. Bernd  |  March 23rd, 2008 at 2:23 pm

    I would download thid very nice plugin from the WordPress Plugin page
    I got an 404 Error.
    Maybe you can repair it? ;-)

  • 10. Rob  |  March 23rd, 2008 at 2:35 pm

    Bernd: Sorry about that. I am in the process of setting up the official plugin pages for the post plugins. It should be fixed shortly.

  • 11. Josette  |  March 23rd, 2008 at 2:46 pm

    Hi Rob! I just moved the post-plugin-library folder and similar post folder to my plugin directory and everything is working well now. Thanks! =D

  • 12. Wolfgang  |  March 24th, 2008 at 12:30 am

    Hi Rob! I had Version 2.3.6 installed (WP 2.3.3/German) and everything was perfect. I now wanted to install 2.5 b5 and did this exactly as described (deactivated it, removed the folder, uploaded the new one with post plugin library) and activated it.
    But there where no similar posts found. Every post had a “None found” under it. Tried to change some setting but without success. Re-indexed – no success. Deinstalled the plugin completely and re-installed it again – no success. Again completely deinstalled it and went back to the old version 2.3.6 which still works fine.
    Any idea? Greetings Wolfgang

  • 13. Rob  |  March 24th, 2008 at 8:51 am

    Wolfgang: That’s very disturbing! Did you download from this site or from the plugin site? If from the external site, did you also download the Post-Plugin Library plugin? I set up the downloads yesterday and I am having problems getting the proper instructions to show…

    I’d be grateful if we could track down this issue.

  • 14. knowlimit  |  March 24th, 2008 at 3:02 pm

    Keep getting this error message when I attempt to enter Similar Posts options: Fatal error: Class ‘admin_subpages’ not found in /home/.neo/site/ on line 44.

    I have followed the instructions deactivated, deleted folder, uploaded both folders plugin (version 2.5 b5) and library into the plugins directory.

    I’ve deactivated, removed folders (plugin and library) and reloaded with no success.

    WP 2.3.3

    Please help.

  • 15. Wolfgang  |  March 24th, 2008 at 4:23 pm

    Well, even tried Version 2.5 b4 from this site and 2.5 b5 from Always installed the Post-Plugin Library, which was only shown as plugin with b5. I tried it with php4. Do you think I should try it with php5 on my webserver? Might there be a problem?

  • 16. Rob  |  March 24th, 2008 at 4:28 pm

    knowlimit: Have you activated the Post-Plugin Library from the Plugins page? It should happen automatically … Can you check on the Plugins page. There should be an entry for Similar Posts and an entry for Post-Plugin Library.

    Thank you for reporting this. It really helps to work towards getting this right.

  • 17. knowlimit  |  March 24th, 2008 at 4:43 pm

    Similar Posts is activated.

    There is not an entry to activate Post-Plugin Library at wp-admin/plugins.php.

    The Post-Plugin Library folder is located at (the four files are inside the folder.

    Both folders are CHMOD 664.

  • 18. Rob  |  March 24th, 2008 at 5:02 pm

    knowlimit: I think I see! Can you download a fresh copy of the Post Plugin Library and try that?

  • 19. knowlimit  |  March 24th, 2008 at 5:26 pm


    After I uploaded the new PPL folder, I checked my plugin page and noticed that the PPL plugin was already activated.

    Similar Posts, as well as Random Posts, is now working perfectly.

    Thanks for your assistance, and plugins.


  • 20. Rob  |  March 24th, 2008 at 5:35 pm

    Wolfgang: Can you follow these links to download the latest versions of both Similar Posts and the Post Plugin Library and then let me know how things stand and we can work out from there what the problem is.

  • 21. Wolfgang  |  March 25th, 2008 at 12:40 am

    Did as requested, but still the same: “None found”. Went again back to the working version 2.3.6.

  • 22. azz  |  March 26th, 2008 at 6:02 am

    Just a feedback.

    WordPress 2.3.1
    Operating System : Linux
    Server : Apache
    MYSQL Version : 5.0.51a-community
    PHP Version : 5.2.1
    Post-Plugin Library: 2.5b11
    Similar Posts: 2.5b9
    Download from

    How i do it:
    Deactivate previous plugin version
    Similar Post –> Post-Plugin Library
    Delete plugin folder from hosting server
    Upload new version and activate plugin
    Post-Plugin Library–>Similar Post
    Working great, no problem at all
    very nice plugin,

    Hope this will help others

    Thanks Rob

  • 23. Rob  |  March 26th, 2008 at 7:53 am

    azz: Thank you.

  • 24. Rob  |  March 26th, 2008 at 4:46 pm

    Wolfgang: 2.5b10 may address the problem you’ve been having–at least it has worked for several other people.

  • 25. Wolfgang  |  March 26th, 2008 at 5:52 pm

    Yes! It works now! What was the problem?
    Love the new options. The plugins brings now even better similar results. Great! Keep up the good work!

  • 26. Rob  |  March 26th, 2008 at 6:32 pm

    Wolfgang: Thanks. The problem was that the database table creation code failed under certain configurations. I’ve tried to make it as innocuous as I can and provided a fallback for versions of MySQL pre-4.1. I hope it will solve all those ‘none found’ issues.

  • 27. Wolfgang  |  March 26th, 2008 at 8:02 pm

    Just clicked through a a few tens of posts and the similar posts really look good :-)

  • 28. Rafael Arcanjo  |  March 27th, 2008 at 11:38 pm

    I had an error:

    Plugin could not be activated because it triggered a fatal error.

    I’d installed Post-Plugin Library 2.5b11 and couldn’t use the Similar Posts 2.5b10.

    WordPress 2.3.3

  • 29. Rob  |  March 27th, 2008 at 11:56 pm

    Rafael: Can you tell me the versions of PHP and MySQL you are using? Can you tell me if the database table ‘wp_similar_posts’ has been created? Thanks.

  • 30. Leona  |  March 28th, 2008 at 8:48 am

    Hi I have the same fatal error problem too. No database wp_similar_posts were created. Am I supposed to create it manually? No rite? I’m using WP 2.2.2

  • 31. Rob  |  March 28th, 2008 at 10:36 am

    Leona: The creation should happen automatically but in some cases it is not. Could you try and create the database manually and let me know what the error message is that appears? The sql command can be found in the first question of the FAQ above…

    Also can you tell me your PHP and MySQL versions, etc. If you don’t know them have a look on the Similar Posts menu (if you can get to it!) and send me a bug report — it will tell me those details.

    Thanks for your time and effort — it really helps to make the plugin work for everyone.

  • 32. Ben Chun  |  March 30th, 2008 at 5:34 pm

    Hi Rob — I jumped versions from 2.0.14 beta all the way up to 2.5b11. I deactivated the old one first and made sure to install the Post-Plugin Library and the Plugin Output Cache before installing and activating the new plugin. However, when I activate the new plugin I get:

    Fatal error: Call to undefined function get_object_term_cache() in /www/blog/wp-content/plugins/similar-posts/similar-posts.php on line 471

    I’m on WP 2.1.3 and PHP 5.2.5. The wp_similar_posts table is correctly created, but remains empty.

    Any ideas? Something left over from the old plugin messing me up? (Like the “similartems” entries in wp_postmeta?) Or something else I forgot to install? Thanks in advance.

  • 33. Kes  |  March 30th, 2008 at 5:37 pm

    Can this plugin display just recent posts by category. I don’t want it to search and all that. I just want it to display the recent posts under a article that all belong to the same category.

  • 34. Keko  |  March 30th, 2008 at 6:03 pm

    Hi Rob, and thanks for your Wp plugins, they make my job easier and my blog more usefull.

    Excuse my english, I’m from Spain.

    Now the problem:

    I deactivated post plugin library and Similar posts, then I updated my blog to WP 2.5 and download the new version of both plugins. When I try to activate then an error message appears:

    Fatal error: Cannot redeclare similar_posts() (previously declared in D:\inetpub\webs\kekopontecom\public\wp-content\plugins\similar-posts\similar-posts.php:33) in D:\inetpub\webs\kekopontecom\public\wp-content\plugins\similar-posts\similar-posts.php on line 33

    ¿Any Idea? Thank you very much, Rob!

  • 35. Tanguillo  |  March 30th, 2008 at 6:09 pm

    I still have the same problem as Keko, even after download the last version and erase the old ones.
    The plugins activate, but In the site, it shows me the message “Post-Plugin Library missing”.

  • 36. Rob  |  March 30th, 2008 at 6:35 pm

    Kes: My Recent Posts plugin will do the trick.

  • 37. Rob  |  March 30th, 2008 at 7:07 pm

    Keko & Tanguillo: I am mystified as to why this happens. It is like the plugin is already installed and it see similar-posts() being defined twice!

    This is my best advice… give it a try and see if it does anything. If you can get to the similar posts options page use the option there to completely remove the plugin. The delete both the similar posts and the post plugin library folders.

    Make sure the plugins page shows they have gone.

    Try deactivating and reactivating another plugin.

    Then upload the post plugin library and activate it.
    Then upload similar posts and activate it.

    If the problem doesn’t go away get back in touch. We can try some changes until we get it working but without knowiing the cause it is frustrating.

  • 38. Keko  |  March 30th, 2008 at 7:25 pm

    It worked for me!
    I just remove the plugin in the options page and then reactivate it. Don’t need to upload them again.

    Thank you very much Rob!

  • 39. Rob  |  March 30th, 2008 at 9:15 pm

    Keko: I’m glad it worked eventually. I just wish I could figure out why the error occurs in the first place.

  • 40. Rob  |  March 30th, 2008 at 9:17 pm

    Ben Chun: Glad to hear the changes got the plugin working again. The next beta contains fixes for versions of WordPress before 2.3 introduced native tagging.

  • 41. mrdeus  |  March 30th, 2008 at 9:49 pm


    First of all: thank you for a great plug-in!

    An issue I’ve been having is that when I write a post I usually write a draft and then edit it some times before publishing it, saving the post between each edit to see the updated preview. It seems that the similar post keywords only are extracted on the first save and aren’t updated when I finally publish the post. Is there a way to force the plugin to re-extract the keywords?

    I’m running WP 2.0.5 and similar posts 2.3.6

  • 42. Rob  |  March 31st, 2008 at 12:50 am

    mrdeus: For your version you can delete the custom field with the keywords and they will be regenerated on the fly.

    I’ll look into the underlying problem.

  • 43. Tanguillo  |  March 31st, 2008 at 1:28 am

    It work! :)
    As keko says, no need to remove the files. Thanks for the advice!
    No I’m happy ;)

  • 44. mrdeus  |  March 31st, 2008 at 1:00 pm

    Thank you! That worked like a charm.

  • 45. Rob  |  March 31st, 2008 at 2:33 pm

    Excellent plugin.

    I’m having an issue with the Similar Posts plugin displaying the same post on every page. It only does it if I have the “Recent Posts” (built-in) widget above your plugin.

    I read your FAQ and you say this is fixed in Wp2.5 (which is what I’m using), could you shed any light on the matter?


  • 46. Rob  |  March 31st, 2008 at 2:38 pm

    Rob: Well… I thought WordPress 2.5 had corrected the issue. Similar Posts needs to know the ID of the visible post it is looking for matches to. The problem is that the built-in Recent Post widget runs its own database query and wipes out that information. I thought that the new version restored its context when it was finished but apparently not.

    All you can do is invert the order or switch to my own Recent Posts plugin ;-)

  • 47. Tanguillo  |  March 31st, 2008 at 4:35 pm

    Hi Rob. I upgrade the plugin to the last version, using the automated method, and it show me the “Fatal error” message again.
    I went to my site and it was a “No related post found” message.
    But I re-index and all work again.
    If I can help you to fix this issue, let me know.

  • 48. Terry Walsh  |  March 31st, 2008 at 10:38 pm

    Here too….

  • 49. Rob  |  March 31st, 2008 at 11:46 pm

    Terry Walsh: If you can get to the similar posts bug report screen can you send me a report. Otherwise can you let me know the versions of PHP, MySQL, etc. and any other details you think might be relevant. I’m trying to chase down the common denominator.

  • 50. Mr.N  |  April 1st, 2008 at 9:14 am

    excellent plugin ..
    i’ll use it in my wordpress 2.5

  • 51. solodelibros  |  April 1st, 2008 at 5:57 pm


    I upgraded your excellent plugin in order to use it with the new WordPress 2.5
    I see that Similar Posts isn’t using the Custom Fields option, and I want to know if it is possible yet to include my own words as I did with the older version.

    Thanks for your help.

  • 52. Rob  |  April 1st, 2008 at 6:31 pm

    solodelibros: Sorry but that ability has been dropped. Instead you can use WordPress’s own tagging to influence the way posts register as similar.

  • 53. Matt K  |  April 3rd, 2008 at 7:08 am

    I’ve been running into this seemingly recurring problem:

    Fatal error: Cannot redeclare similar_posts() (previously declared in /home/content/m/a/t/mattkastner/html/blog/wp-content/plugins/similar-posts/similar-posts.php:33) in /home/content/m/a/t/mattkastner/html/blog/wp-content/plugins/similar-posts/similar-posts.php on line 33

    I’ve done the reinstall and the Post-Plugin Library is already installed. No similar posts sql entry has been made. I was going to try to manually enter the SQL query, but I can’t find the specific instructions for that.

  • 54. Rob  |  April 3rd, 2008 at 10:34 am

    Matt K: This infuriating error happens on a minority of sites and I have not yet tracked down the cause. Can you do a complete uninstall (from the settings screen if you can get there) before reinstalling. I’d even go so far as to delete the files before reinstalling. This has worked for some of the afflicted users.

    The FAQ (above) has the SQL to create the needed table manually. I’d be glad to hear what works!

  • 55. Simon  |  April 3rd, 2008 at 1:43 pm

    Fatal error: Call to undefined function: suppress_errors() in /usr/www/users/investe/altx/reports/wescoal/wp-content/plugins/similar-posts/similar-posts-admin.php on line 405

    Plse cud u offer some advice?

  • 56. Matt K  |  April 3rd, 2008 at 5:53 pm

    Thanks for the quick response Rob. Unfortunately I have already tried the technique you mentioned many times. My site is hosted on GoDaddy (I had to do a little workaround to install WordPress at all) so I am wondering if it might have something to do with that.

    As far as the SQL you mentioned in the FAQ, I can’t find which entry you are referring to. I would assume it would be in the first question, but I don’t see it. I’m pretty decent at muddling my way through this stuff, but I must admit that I am pretty fresh to SQL. Thanks again.

  • 57. Rob  |  April 3rd, 2008 at 6:09 pm

    Simon: the latest posted version should fix that issue.

  • 58. Rob  |  April 3rd, 2008 at 6:11 pm

    Matt K: I’ve just uploaded a newer version that might make a difference.

    The sql, by the way, is in the second FAQ entry.

  • 59. Matt K  |  April 3rd, 2008 at 7:15 pm

    Looks like I won’t be needing to get into the SQL after all. The new version took care of my problem. Its working like a charm. Thanks for everything.

  • 60. simone  |  April 5th, 2008 at 11:28 am

    nice plugin, works on my web site

  • 61. Mark Evans  |  April 5th, 2008 at 2:37 pm

    Love the plugin – easy to install and configure. One small question: Does the plugin work for posts after installation or can it provide links to previous posts. Right now, I don’t see any Similar Posts on earlier entries.


  • 62. Rob  |  April 5th, 2008 at 3:18 pm

    Mark Evans: It should work for all the posts in your database. Try re-indexing from the Manage | Similar Posts screen.

  • 63. Mark Evans  |  April 5th, 2008 at 6:50 pm

    Thanks, Rob. One last question: I now need to insert this:

    Where should it go within the index.php or single.php?


  • 64. Mark Evans  |  April 5th, 2008 at 9:02 pm


    Figured things out, and installed the plug-in on another blog. Thanks for creating it!

  • 65. Rob in Denver  |  April 5th, 2008 at 9:24 pm

    Hi… I also love this plug. I’m getting a similar syntax non-fatal error:

    WordPress database error: [You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'LIMIT 1' at line 1]
    SELECT title, content, tags FROM wp_similar_posts WHERE pID= LIMIT 1

    I’ve tried many of the troubleshooting tips you’ve given and I still get the error. Also, you mentioned to another commenter to submit a bug ticket from the Settings page. The only settings page I get is the General Settings page (but I recall a page that allowed additional customization).


    Thanks in advance.

  • 66. Rob  |  April 5th, 2008 at 9:52 pm

    Rob in Denver: I’ve found and fixed the bug and it’ll be in the next beta. In the meantime if you want to change the code yourself look in similar-posts.php for the function terms_to_match(…). Add the following line as the first line of the function, even before the globals statement :

    	if (!$ID) return array('', '', '');

    That should do it.

  • 67. Ben McCann  |  April 6th, 2008 at 12:26 am

    I love the idea of this plugin, but am having some trouble getting it to work. I have a development site up at and every single story shows the same related posts. Any ideas on what my be causing this?
    I tried to process the posts to see if that made a difference, but I’m not sure whether it worked. I don’t see anything stored in the database, but am not quite sure where to look. Another comment mentioned wp_similar_posts and that table does not exist.


  • 68. Rob  |  April 6th, 2008 at 1:13 am

    Ben McCann: First, try deactivating and then reactivating. It should create ‘wp_similar_posts’ table (or with whatever prefix you use).

    If it doesn’t create the table you can create it manually (try the first or second FAQ entry above).

  • 69. Rob in Denver  |  April 6th, 2008 at 3:34 am

    @Rob: Thanks for the bug fix. Attempted, but now I get the mysterious previously declared fatal error. Tried deactivating then deleting then reinstalling to no avail.

    But what happened might lend some insight to the aforementioned fatal error.

    There’re two places in the plug in where terms_to_match(…) appears:

    1. At about line 185. I put the code snippet here and my original non-fatal syntax error still popped up.
    2. At about line 78. I dropped the snippet in here… and that’s when the fatal error starts.

  • 70. Rob  |  April 6th, 2008 at 10:34 am

    Rob in Denver: Just insert the snippet in the function and not at ~78.

    It should look like:

    function terms_to_match($ID, $num_terms = 20) {
    	if (!$ID) return array('', '', '');
    	global $wpdb, $table_prefix;

    Please let me know if that fixes the problem or not.

  • 71. Jinge  |  April 6th, 2008 at 11:31 am

    I want the output in every post, not in a widget. How to do that?

  • 72. Jinge  |  April 6th, 2008 at 11:33 am

    I want the output in every blog post, not in a widget. How to du that?

  • 73. Rob  |  April 6th, 2008 at 3:10 pm

    Jinge: You need to insert the call to similar_posts() somewhere in your theme files. Where that should be depends on the theme you are using and where you want the similar posts list to appear. But, for example, let say you wanted the list directly after the post content on pages that are showing single posts… your theme probably has a file single.php. Open it for editing and you’ll probably see somewhere in the middle the line:

    <?php the_content();?>

    You could then insert after that line the line:

    <?php similar_posts(); ?>

    If that isn’t quite where you want it, play around until you have the right place. You might have to tune your style sheet to get the exact look you want.

  • 74. Rob in Denver  |  April 6th, 2008 at 4:58 pm

    @Rob… that did it. I just had the snippet in the correct function., just in the wrong line.


  • 75. Yvonne  |  April 7th, 2008 at 8:12 am

    Hi Rob, I also got this error when upgrading similar_posts.

    Fatal error: Cannot redeclare similar_posts() (previously declared in blah/public/wp-content/plugins/similar-posts/similar-posts.php:33) in blah/public/wp-content/plugins/similar-posts/similar-posts.php on line 33

    Here’s my setup: I have 6 active WordPress blogs on the same server. 5 of them share one database. The problem occurred on the 6th blog (url above), which shares a database with an inactive WordPress blog. The active blogs are all running WP 2.5. The inactive blog is still on 2.3 or something like that.

    I used the upgrade automatically feature to upgrade Similar Posts. It went off without a hitch on the first 5 blogs. On the sixth blog, I got the error when it tried to re-activate. It may be worth mentioning that this is the only blog I didn’t select “Use SSL” when setting up the FTP connection.

    The error persisted, no matter how many times I de-activated/deleted the plugin and directory. De-activating/deleting post-plugin-library didn’t help.

    What finally made the error go away was removing the plugin via Settings, and then re-activating.

    Please e-mail me if you want more details about my setup. Though I’m not sure the setup matters that much — maybe it’s something in the similar_posts settings themselves that’s causing the problem, given that the problem gets fixed if you wipe them…

  • 76. Rob  |  April 7th, 2008 at 8:55 am

    Yvonne: I’ve sent you an email following up. Thanks for the detail.

  • 77. CWF Game Cast  |  April 7th, 2008 at 10:07 pm

    Rob: You should be aware of

    I’ve posted in that, as arickrol, for a major problem I’m experiencing with custom fields. Your plugin, Similar Posts, is having problems too. It seems to be a couple hundred, no exagerration, custom fields that have duplicates. Others have the same problem with WP 2.5 but don’t know if they use your plugin.

    It has caused me to abandon your plugin so I can try to keep using WP 2.5 (the only way to fix my tags show as numbers issue). I’ve contacted other plugin authors that this deals with. Hopefully everyone can find solutions for their own plugins.

    Next stop for me is the podPress people to tell them about the issue too.

  • 78. Rob  |  April 8th, 2008 at 12:05 am

    CWF: I’m not sure what you mean by custom fields that have duplicates? Similar Posts 2.5 no longer uses uses custom fields to store data. The only use it makes is to allow the {custom} tag to access a chosen custom field.

    Can you describe exactly what is happening?

  • 79. CWF Game Cast  |  April 8th, 2008 at 12:49 am

    I deleted all the Similar Posts custom fields to defray the error. But, I had a few hundred custom fields (when making a new post they show at the bottom) and each one listed a bunch of words.

    I believe they were words used to find similar posts on the blog. But, many of the entries consisted of saying a single word repeatedly. For example, one said “gaming gaming gaming gaming gaming wargaming wargaming wargaming wargaming war war war war cwf cwf cwf cwf” and etc.

    I only received the errors from Firefox, and Safari, when I upgraded to WP 2.5 RC1 and it became much worse when I upgraded to WP 2.5. It is a known bug in WP. But, it seems it only happens with certain plugins. I don’t know the complete list and unfortunately don’t have more information.

  • 80. Rob  |  April 8th, 2008 at 12:59 am

    CWF: What you describe is not in itself an error. The OLD versions of Similar Posts stored keywords in a custom field called ‘similarterms’ and — because of the way the MySQL full text search works — allowed for the varying frequency of keywords by repeating them.

    What is strange is that those fields persist after installing Similar Posts 2.5. The installation routine should have deleted all of them. If you want to do it manually the sql is:

    DELETE FROM `wp_postmeta` WHERE meta_key = 'similarterms'

    You might have to change the table prefix.

  • 81. CWF Game Cast  |  April 8th, 2008 at 1:01 am

    The error is the one given by Firefox. But, the odd thing is not that terms are repeated inside each custom field but that there is a repetition of custom fields.

    When one of them lists “war” repeatedly there is another custom field in the list that also lists “war” repeatedly. Somehow they got duplicated.

  • 82. Rob  |  April 8th, 2008 at 1:09 am

    CWF: If you are/were using Similar Posts v2.5 there should be no such custom fields and the plugin has no code to do anything with custom fields apart from the one installation routine to delete them.

    If you get rid of the lot of them and do a clean install of Similar Posts I’d be gobsmacked if they came back…

  • 83. Chris Masse  |  April 10th, 2008 at 12:15 am

    Thanks for this great plugin.
    There is little problem that you should be aware of. Please, do read what another plugin author said here:
    See comments #299

  • 84. Rob  |  April 10th, 2008 at 12:53 am

    Chris: I’m aware of the potential conflict with plugins which replace the admin menus. Their usual technique is to make the original submenu invisible with display: none. That’s why my plugin uses inline styles to reset display. Ozh’s replacement menu uses a different technique: he uses jQuery to actually remove the html of the submenu. Since there is only supposed to be one id of submenu only the first submenu gets overwritten. At least on the systems and browsers I have available.

    I have posted about the technique I use for the subpages including, in the last paragraphs, the hazards of ‘stealing’ the submenu id.

    Can you tell me what system and browser you are having problems with so I can do a workaround?

  • 85. Chris Masse  |  April 10th, 2008 at 2:27 pm

    Thanks for your reply.
    1. I don’t use “Admin Drop Down Menu” anymore. I now use both “WordPress Admin Bar” and “Lighter Admin Drop Menus”. And they work fine with “Similar Posts”.
    2. That said, tell me what I should do to help you.
    3. I use FireFox
    I use Windows ME.
    I use WP 2.5.
    My plugins:
    (Since last time, I have just dumped “Bad Behavior” for “Spam Free”.)
    Chris Masse

  • 86. Rob  |  April 10th, 2008 at 9:31 pm

    Chris Masse: Well, the only thing that stands out from your response is Win ME… but I doubt that is anything to do with it.

    I like the way that the current subpages adapt to the style of the admin interface — stealing the submenu id makes that so easy. There is a javascript way of manipulating style sheets to copy styles but it doesn’t have complete browser coverage. The final fall back would be to forget the chameleon-styling and just inject some nondescript CSS…

    Or I could try and convince Ozh to hide the old submenu a different way.

  • 87. Angus  |  April 11th, 2008 at 1:25 am

    Help!! Upgraded to 2.5b16 this morning and now my blog is screwed up. I’m using WordPress 2.5

    After I upgraded to 2.5b16:

    1) it showed 500 error so I deactive it and reactive it then it worked for a while. Then it was working again so I deactive with wp-cache plug-in and it worked again.

    2) Now my footer is gone. I didn’t touch anything since (1) in the morning. It was still there in the afternoon but it’s all gone now.

    3) Now my some of my right hand side widgets are gone. Can’t add them back at all.

    Please Help!!!!

  • 88. zag  |  April 11th, 2008 at 3:27 am

    I get a the typical:
    Internet Explorer cannot display the webpage

    When clicking on Recreate Index

    WordPress 2.5
    Similar Post 2.5b16

    If I hit f5 or refresh it gets back to the Options page for Similar Posts. Anyone?

  • 89. Rob  |  April 11th, 2008 at 8:08 am

    Angus: I’ve responded by email asking some debugging questions. Thanks for your help.

  • 90. Rob  |  April 11th, 2008 at 8:18 am

    zag: Can you send me a bug report via the Options page for Similar Posts? That will give me some extra debugging information. Can you tell me the version of IE too?

    Meanwhile… do you have the latest version of the Post-Plugin Library installed? Have you tried uninstalling and reinstalling?

    Please keep me informed so we can fix this.

  • 91. Dominik Koza  |  April 11th, 2008 at 12:59 pm

    Wordpres 2.5 and everything works just fine :) thx.

  • 92. zag  |  April 11th, 2008 at 11:55 pm

    I’ve upgraded to latest version, still same problem, is there any way to force the ReIndexing via command line in a shell console instead of wordress control panel.?

    Regards nice work.

  • 93. zag  |  April 11th, 2008 at 11:56 pm


  • 94. zag  |  April 12th, 2008 at 12:33 am

    just found out, not only does not reacreate index, it deletes any entrie on table wp_similar_posts. :(

  • 95. zag  |  April 12th, 2008 at 1:58 am

    foudn the problem, solution, I raised the memory_limit on php.ini because I have to many records on wp-post,

    tahnk you

  • 96. Charles R  |  April 12th, 2008 at 6:00 am

    I was wondering how easy it is to change the font color of the generated links(Similar Posts)?


  • 97. Rob  |  April 12th, 2008 at 8:13 am

    zag: Good morning! A lot went on while I was sleeping! I’m glad you found the issue and the solution. Can you tell me what the initial memory limit was and what limit made the error go away? Oh and how many posts does your blog have?


  • 98. Rob  |  April 12th, 2008 at 8:17 am

    Charles R: It is very easy… You just need to apply some CSS styling. If the default markup is specific enough you can just add to your theme’s stylesheet. If not you can apply a class in the plugins output template, e.g., to the the prefix:
    <ul class="posts-list">

  • 99. Vortrack  |  April 12th, 2008 at 5:53 pm

    I’m using the default setting but I can’t see ANYTHING that related to my post though they are the same.

  • 100. 2g  |  April 12th, 2008 at 8:40 pm

    I have a “Post-Plugin Library missing” error. How can I fix it?


  • 101. Rob  |  April 12th, 2008 at 10:16 pm

    2g: Just download the library and install.

  • 102. [/root.]  |  April 13th, 2008 at 3:00 am

    I’m using this template

    {custom:thumbnail-small} {link}

    How do I check if the custom field is filled or not? If there is not value in the custom field then it makes an unnecessary space before {link}. Thanks.

  • 103. Rob  |  April 13th, 2008 at 8:08 am

    [/root]: Probably the easiest way is to bypass {custom} and use another {php} tag! Try:

    {php:$thumb=get_post_meta($result->ID, 'thumbnail-small', true);if ($thumb)echo $thumb.' ';}

  • 104. David  |  April 14th, 2008 at 4:44 am

    Upgraded to 2.5b20 from 2.3

    WP 2.5

    “None Found”

    Worked perfect before with 2000+ articles

    Tried evrything

    In the DB (MySQL 5.+) after config plugin no DB tables are populated within anything.

    Went back to 2.3…same problem persists.

  • 105. Rob  |  April 14th, 2008 at 11:30 am

    David: A number of questions… did you download the Post-Plugin Library which 2.5 needs? Did you use the Manage page to index your posts? Did you get rid of the old version’s file before upgrading?

    Those are the most obvious causes of Similar Posts not showing any posts.

    Please get back to me and we’ll get this sorted out. Similar Posts 2.5 has a bug report screen under the settings menu which might provide some useful clues.

  • 106. rufus  |  April 15th, 2008 at 12:22 am

    awesome plugin, everything is working fine for me, except today i activated the {views} for the similar posts and its only displaying ARRAY. Post views work fine on my sidebar with another plugin. im using wp 2.5, any advice on why it displays array instead of a number?

  • 107. Rob  |  April 15th, 2008 at 10:28 am

    rufus: The {postviews} output template tag relies on you having a plugin installed to do the post view counting. It works with several of the best known such plugins but not all. Which one are you using?

    However, if Similar Posts can’t find a plugin to work with it should return zero, not ARRAY, so maybe there is a bug in my code. Let me know which post view plugin you are using and I’ll look into it.

  • 108. rufus  |  April 16th, 2008 at 6:28 am

    im using WP-PostViews, you can find it here

  • 109. Nathan Cain  |  April 16th, 2008 at 2:58 pm

    When I click on any of the option tabs in similar posts OR recent posts, I get an error that says “Cannot Load Recent.” OR “Cannot Load Similar”

  • 110. Rob  |  April 16th, 2008 at 3:08 pm

    Nathan Cain: Is this a new installation of these plugins? If it was an update make sure you removed the old plugin folders. Have you downloaded and installed the Post-Plugin Library whcih the plugins now require?

    Also try simply deactivating/reactivating the plugins. Remember to go to the Manage >> Similar Posts page to index your blog.

  • 111. David  |  April 16th, 2008 at 3:11 pm

    Further to #104/#105

    Entirely my fault. Duh.

    I went to Settings > Similar Posts and set all the options but not clearly realizing I also had to go to Manage > Similar posts.

    May i suggest placing all options within one UI location in future?

  • 112. Nathan Cain  |  April 16th, 2008 at 3:21 pm

    Rob – This is a new installation. I downloaded and activated the post-plugin library first. I reindexed under manage>similar posts. I deactivated and reactivated these plugins and I am still getting the errors.

  • 113. Rob  |  April 16th, 2008 at 3:22 pm

    David: I’m glad you solved the problem! I was worried by your initial description–I thought we had obliterated your blog!

    The indexing thing is a chore. Originally, I had the installation routine do a basic index but it failed on some odd systems with very weird and uninformative error messages so now I leave it to the user to do a manual index. As you found out that’s unsatisfactory for several reasons.

  • 114. Rob  |  April 16th, 2008 at 4:40 pm

    Nathan: I am puzzled. Can you tell me anything about your system? Apache? Versions of PHP, MySQL, etc. I have had one previous report of the subpages not working with a certain variety of IIS.

    Also are you using wp-cache or an admin drop menu plugin?

    Can you check to see if a table has been created called ‘wp_similar_posts’ and if that table has been filled with as many rows as the wp_posts table?

    I hope we can resolve this speedily.

  • 115. gero  |  April 16th, 2008 at 11:16 pm

    Hello Rob,

    it’s not a bug, but a thing that should be changed in the next version:

    If you include the Similar Posts in the rss-feed, there is no option to set (or translate) the string before the tag. It says hard-coded “Similar Posts:”

    It would be great, to have the possibility to change this string like in the other options-page.


  • 116. Rob  |  April 17th, 2008 at 4:47 pm

    gero: Which version are you using? In v2.5 when you choose to have similar posts’ output to your feeds a new setting menu is created which lets you tailor the output to feed as much as you want, including changing the string before the tag.

  • 117. Mara Mei  |  April 18th, 2008 at 5:12 am

    This plugin work perfectly at my blog. Thank you.

  • 118. rufus  |  April 18th, 2008 at 6:20 am

    Rob were you ever able to get the postviews counter on your plugin to work with the wp-postviews plugins i linked above? the Array message can be seen on my blog. wp-postviews can be found here thanks for all your hard work.

  • 119. Rob  |  April 18th, 2008 at 9:41 am

    rufus: Sorry an email to you must have gone astray. It looks like Lester updated his plugin so the code had to be changed for the next version. In the meantime you can edit post-plugin-library/output_tags.php if you wish and make the patch.

    Round about line 380 you’ll find the code to handle postviews, update it to:

    	else if (function_exists('the_views')) {
    		$count = get_post_custom($result->ID);
    		$count = intval($count['views'][0]);

    See if that does any good.

  • 120. gero  |  April 18th, 2008 at 10:40 am

    Oh, sorry,
    yes, perfect! There are feed option. I just haven’t noticed, that they appear not in the similar feeds option, but in extra settings.
    Everything is perfect :-)

  • 121. john  |  April 19th, 2008 at 2:45 am

    I placed the recent_posts on the sidebar and all works well. What would I need to do to get the same list to show up on my homepage which is outside of wordpress.
    So say public_html/wordpress –> wordpress blog
    I want to access it from public_html/index.php

  • 122. Rob  |  April 19th, 2008 at 10:01 am

    john: I’m not sure! You will have to ‘include’ the plugin and at least some of the WordPress files — which I am not sure. Maybe the codex has something on the subject?

  • 123. Jenny  |  April 19th, 2008 at 1:20 pm

    The plugin is working, but each post is only picking up that same post as a related site.

    I’m not sure how to set it up really whithi the settings part. I have recreated my index.

  • 124. Rob  |  April 19th, 2008 at 3:52 pm

    Jenny: Can you make a bug report from the Similar Posts setting screen … that might give me a clue as to what is going on.

  • 125. Crystal  |  April 21st, 2008 at 9:35 pm

    I just upgarded to 2.5b22. I followed the steps as stated in the instructions and now no post will show up. It says ‘None Found’ I tried deactivating and reactivating and I still get the same thing. It worked fine before I upgrading to the new version. I went though all the setting, everything is fine. What did I do wrong?

  • 126. Rob  |  April 21st, 2008 at 10:30 pm

    Crystal: Have you indexed the posts? Always worth asking! Perhaps you could submit a bug report from the settings page which will give me some extra information. Could you also tell me what version you upgraded from?

  • 127. Crystal  |  April 21st, 2008 at 10:43 pm

    I did index. Honestly I can’t remember what version I had before I upgraded. It was a more recent one, I know that, as I usually check my plugins a few times a month and upgrade them when needed. I just submitted a bug report.


  • 128. Rob  |  April 22nd, 2008 at 12:08 am

    Crystal: I think I know what the problem is. You have the plugin set to match both categories and tags and that is a very strict condition. Try unsetting those options and see if the related posts come back.

    This is a change of behaviour from previous versions where — somewhat illogically — if such matching yielded no hits the plugin reverted to just ignoring the tags and/or categories.

  • 129. Crystal  |  April 22nd, 2008 at 1:04 am

    I unset the options you said and it works now. I had those options set-up before and it worked. Oh well….as long as it’s back up and running I’m happy. I’ve used this plugin for all my blogs, I love it. :)

    Thanks for your fast response helping me out.

  • 130. Max  |  April 22nd, 2008 at 10:02 am

    I’m using the plugin on wordpressMU V 1.2.5 I get the same output on every page. I’m not sure where to go form here. Thanks in advance for any help you might be able to provide.

  • 131. Rob  |  April 22nd, 2008 at 12:18 pm

    Max: I must confess I have been wanting to explore how to make sure my plugins work properly with WPMU for some time but I have never gotten to it.

    Do you know of any differences I should take into account? Any, perhaps you could make a bug report from the options/settings page as that will at least give me some information that might be useful.

  • 132. Paul  |  April 22nd, 2008 at 2:23 pm

    Just upgraded post-plugin-library to the latest, whenever I post or edit a post, I receive this error.
    Warning: exec(): Unable to fork [tasklist /FI "PID eq 10152" /FO LIST] in ….\wp-content\plugins\post-plugin-library\common_functions.php on line 441

    I downgraded to an earlier version, and that resolved this problem.
    btw. great plugins.

  • 133. Rob  |  April 22nd, 2008 at 3:24 pm

    Paul: That’s due to a misplaced bit of code. I’ll have it fixed shortly. Thanks for the heads up.

  • 134. Max  |  April 23rd, 2008 at 1:01 am

    Ok, I’ve just tested a couple of things and found that the problem is not caused by wordpressMU it’s actaully theme related. I’ve been testing with an old theme in MU and it works like a charm.

    Now I am not sure how to fix the problem so I have had to disable the plugin again. Why would a theme cause the pugin to pull the same posts on – the theme is quite popular – try it out and I think you will be able to see the problem straight up.

  • 135. Rob  |  April 23rd, 2008 at 10:51 am

    Max: It could happen if the them has multiple ‘loops’. Similar Posts has to find out somehow which post is the current one so as to compare it to others for similarity. It gets the current post’s ID by looking at the $post variable which is set in the WordPress loop. If theme or plugin or widget runs a second wp-query/loop without restoring its context Similar Posts will have the wrong ID play with. This problem can occur easily with widgets since some of the built-in widgets don’t properly clean up after themselves (though the code has attempted to since 2.5).

    There is no need for themes, plugins etc. to make this mess as Ronald Huereca explains.

  • 136. Jenny  |  April 23rd, 2008 at 11:01 am

    I changed themes and before that the plugin worked fine. Now it is suddenly appearing in a widget, not that I mind.

  • 137. Paul  |  April 23rd, 2008 at 11:27 pm

    Rob: Thank you for your great plugins. I just upgraded to v23 of post-plugin-library and all is well. Thank you, again.

  • 138. Cho Kwan Hee  |  April 24th, 2008 at 2:50 am

    I finisihed to install in my blog just before. And it works well.

    It is what I’ve been looking for.


  • 139. Gareth Stack  |  May 1st, 2008 at 7:29 pm

    I’ve installed Posts Plugin Library on WordPress 2.3.3. But when I try to install similar posts I get the following error

    Warning: require_once(/home/.fenne/dbspin/ [function.require-once]: failed to open stream: No such file or directory in /home/.fenne/dbspin/ on line 551
    Fatal error: require_once() [function.require]: Failed opening required '/home/.fenne/dbspin/' (include_path='.:/usr/local/php5/lib/php:/usr/local/lib/php') in /home/.fenne/dbspin/ on line 551

  • 140. Rob  |  May 2nd, 2008 at 10:58 am

    Gareth Stack: It seems likely that you haven’t uploaded the languages folder inside the similar-posts folder.

  • 141. Sue  |  May 3rd, 2008 at 2:44 am

    Hi Rob,
    I am using the thumbnail option with similar posts and love the result, with one glitch – for youtube posts, there is no thumbnail. Is there a workaround for this?

  • 142. Rob  |  May 3rd, 2008 at 10:31 am

    Sue: I’m afraid not since youtube videos are not images. There may be a way extend the {image} output tag without too much trouble or overhead … I’ll look into it.

  • 143. Rob  |  May 3rd, 2008 at 11:00 am

    Sue: There seem to be so many ways to embed videos — many of them non-standard — that I think you are out of luck for the near future.

  • 144. djvibe  |  May 8th, 2008 at 10:36 am

    Any language for chinese? where can I get this..

  • 145. Naveed Taj Ghouri  |  May 8th, 2008 at 1:09 pm

    I have tried everything, DB table is there, i uploaded library plugin first then this one, activated them, put string in my post but it is causing a Fatal error, although its activated and configuring well.. wat to do?

  • 146. rosa de paz  |  May 8th, 2008 at 11:44 pm

    Please! i do everithing that u said but i only find NONE FOUND,
    I go to the edit plugins, and chek the code that you put… but it don{t work… can you please tell me what happend??
    i have the wordpress 2.5

  • 147. gero  |  May 9th, 2008 at 6:55 am


    I’m using WP 2.5 and the newest version 2.5b26 of the plugin.

    Since – I can’t say the version exactly – I’ve noticed, that the results of the similar posts are not as good as they used to be, although I have not changed the settings.

    I also noticed a strange thing: if I recreate the index with “manage the index” the results under some postings are quite strange. I know that there are postings, which are quite more similar, but they do not appear.

    If I than open this posting and just save it again (without changing anything) the similar posts shown under it are much better now.

    How can it be, that the results are different?


  • 148. nonhocapito  |  May 9th, 2008 at 10:03 am

    This plugin is fantastic.

    Only problem… because I have another plugin that modifies my feeds, every time I upgrade your plugin I have to manually edit line 560 (or near that line) from this

    if ($options['feed_active'] === 'true') add_filter('the_content', 'similar_posts_for_feed');

    to this

    if ($options['feed_active'] === 'true') add_filter('the_content', 'similar_posts_for_feed', 99);

    because the other filter must come first (long story).

    well, it would be awesome to have this in the options! :)

  • 149. Tony  |  May 9th, 2008 at 6:19 pm

    I was wondering… how could I display similar posts on my 404 page? When Google sends people to a 404 page, I would like the 404 page to display posts similar to the one that was being searched for through Google.

  • 150. Rob  |  May 10th, 2008 at 10:23 am

    djvibe: There are no stopword/stemmer files for Chinese for a couple of reasons. First, I know no Chinese and don’t even know whether the concept of stopwords etc. is relevant. Second, I do know that the MySQL full-text index the plugin uses has trouble with the Chinese, Japanese, and Korean languages because they don’t use spaces to separate the text into words.

    If you can shed any light on these issues I would be very happy to add support for the CJK languages.

  • 151. Rob  |  May 10th, 2008 at 10:32 am

    Naveed Taj Ghouri: Thank you for your comment. I have just visited your site and I think I might know the problem: the text in your posts seems to be presented as images. Is that correct? If it is then Similar Posts would have no text to index. It should however be able to give matches based on your tags and titles and if it is giving a fatal error I need to fix that.

    Can you submit a bug report from the Similar Posts settings page? It will give me a little extra information that might help. Thank you.

  • 152. Rob  |  May 10th, 2008 at 10:35 am

    rosa de paz: Please make a bug report from the plugin’s settings page and it will give me something more to go on. Thanks.

  • 153. Rob  |  May 10th, 2008 at 10:37 am

    gero: You are right! I investigated and found a bug in the bulk indexing of tags that isn’t present in the indexing of individual posts. When you save a post it gets reindexed and the matches suddenly get better. I have fixed the bug and will be posting an update shortly. Thanks for finding the problem!

  • 154. Rob  |  May 10th, 2008 at 10:41 am

    nonhocapito: I can understand how irritating that must be. It feels a bit bit technical to have as an ordinary option. Would it satisfy you to have it as a ‘hidden’ option you can get at from the global options.php?

  • 155. Rob  |  May 10th, 2008 at 10:52 am

    Tony: As it stands, Similar Posts needs to have a post to find similarities to, so it can’t be done. Since searches tend to be on short phrases or a few keywords my first thought is that similarity might not work very well — a simple site search might be better.

    What do you think? If the idea has some merit I’d be glad to look into implementing it.

  • 156. Jeremy  |  May 10th, 2008 at 6:12 pm

    Rob, thanks for the great plugin. I am using it to show 5 titles of similar posts on my single post page. Is there anyway to have the output include rel="nofollow" so that the page rank from the post is returned only to the home page?


  • 157. Rob  |  May 10th, 2008 at 8:52 pm

    Jeremy: You just have to build the link yourself, i.e., instead of


    <li><a href="{url}" rel="nofollow">{title}</a></li>

    You can also include a title attribute if you wish.

  • 158. gero  |  May 11th, 2008 at 6:01 pm

    Hello Rob,
    just installed version 2.5b27 and rebuild the index.
    Now the similar posts really look great again! Thanks for the bugfix.

    My advice is, that everybody should rebuild the index (options -> manage the index), to get better results.


  • 159. Rob  |  May 11th, 2008 at 6:37 pm

    gero: I spotted another bug — if you use the extended character option — and uploaded v2.5b28 to fix it.

    The new version also contains an experiment in handling Chinese, Korean, and Japanese text.

  • 160. Mark @ News Corpse  |  May 11th, 2008 at 10:56 pm

    Hi Rob,

    I just upgraded both WP and Similar Posts and I have 2 questions.

    1) I have enabled the sort order on date-descending, but the output does not display sorted that way.

    2) I understand that the similarterms custom field is now in a table. I used to edit that field frequently to improve results. Is there no way to do that now? Could an edit feature be added? Tagging is not really a comparable replacement for editing terms. For one thing, you can’t remove terms that way.

    Thanks for the great plugin. I hope you can help with these issues.

  • 161. Tony  |  May 12th, 2008 at 6:16 am

    Rob, I can get the string.

    $uri = $_SERVER['REQUEST_URI'];
    $uri = rtrim($uri, '/');
    $new_string = str_replace("/", " ", $uri );
    $final_string = str_replace("-", " ", $new_string);

    … and I can pass the string to a WordPress search, albeit, it is not automatic.

    <form method="get" id="searchform" action="">
    <input type="text" value="<? echo $final_string; ?>" name="s" id="s" >
    <input type="submit" id="searchsubmit" value="Search" >

    However, I would like to pass along the string to the similar posts plugin to return “Posts that you might have been looking for ,,,” on the 404 page itself.

    What do you think?

  • 162. gero  |  May 12th, 2008 at 7:09 am

    Hello Rob,
    my blog is in german (with umlauts) but I never used the extended character option. I never noticed any big differences in the results. I switched it on now and yes, I must say that after reindexing, the results got again a bit better.
    I love your plugin very much. It is quite amazing, how it finds similar posts without making any manual connections. Great!


  • 163. Mark @ News Corpse  |  May 12th, 2008 at 7:21 am

    Hi again Rob.

    I figured out the sort problem on my own (I added ‘raw’ to the date format), but I would still like to know if anything can be done about editing the terms.

    I was able to significantly improve the results by manipulating the similarterms in the custom field. I already miss not being able to do that anymore.

    (I mistakenly posted this in comments on a different post on your site. Sorry for the repeat)

  • 164. Rob  |  May 12th, 2008 at 10:21 am

    Tony: You’d have to hack the function sp_terms_to_match. Right now it takes the ID of the current post and gathers terms to put into the search. You could instead inject your own terms.

    I’ll be interested to see what you come up with!

  • 165. Rob  |  May 12th, 2008 at 10:22 am

    gero: Thanks!

  • 166. Rob  |  May 12th, 2008 at 10:28 am

    Mark @ News Corpse: I missed the first comment somehow. I’m glad you figured it out.

    There’s now way to edit the terms now as they are generated on the fly. Does the use of tags not help?

  • 167. Rob  |  May 12th, 2008 at 10:45 am

    Mark @ News Corpse: Sorry Mark. I just found your original comment in spam and brought it back to life. Please discount my mention of tagging above!

    The table you mention doesn’t exactly store the ‘similar terms’ — rather it stores a pre-processed representation of post content, title, and tags. When it comes to query time, that representation for the current post is further processed to generate the ‘similar terms’ which are then compared with the representations for every other post. Editing the table is possible but you would be editing both the search terms (if they were judged significant) and the text to be searched.

    If you want to experiment load up phpMyAdmin (the wp plugin is very helpful) and see if editing does what you want it to. I’d be interested to know the answer.

  • 168. Mark @ News Corpse  |  May 12th, 2008 at 5:06 pm

    Thanks for your response (and for finding my lost question).

    If I understand you, it seems the whole method of operation has changed from previous versions. But let me give you some examples of why access to search terms was useful for me.

    1) There were often multiple duplications of words in similarterms. I sometimes saw a word repeated 7 or 8 times so I would remove some of the duplicates.

    2) The plugin would sometimes pick up words that were not relevant. For instance, in a post about the cost of groceries, the sentence: “My sister paid $3.00 for a quart of milk,” might index milk, quart, paid, and sister. But “sister” isn’t useful for similarity in this context. Plus it could match it with another post about a nun. So I would remove “sister” and get better matches.

    3) I could add terms that might not even be in the post so that it would use them to match other posts that I knew also had those terms. I wouldn’t want to clutter up my tags with these sort of words.

    I know similarity matching is part science, part magic, and nothing will be perfect. You’ve done a damn nice job of it. One idea I had is to have the plugin produce a display of what terms it’s indexing. Then allow a custom field for the user to input additional search terms and terms to exclude (preceded by a minus sign). Then the user could fiddle with the results without having to leave the post to edit the DB.

    Does any of this make sense?

  • 169. Mark @ News Corpse  |  May 12th, 2008 at 5:13 pm

    One more thing. In the previous version I noticed that the plugin would set the search terms when WordPress autosaved the post – even if I was not finished writing it. So, many terms didn’t get into the index unless I added them later. However, if I wrote the whole post without entering a title, this would not happen because it didn’t get autosaved until the title was entered. I guess that’s a WP thing, but it definitely affected the plugin’s choice of search terms.

    Does that play into the current version of Similar Posts in any way?

  • 170. Joe  |  May 12th, 2008 at 5:24 pm

    Great Pluggin! Thanks a bunch!

  • 171. Rob  |  May 12th, 2008 at 10:54 pm

    Mark: Last point first: yes WordPress brought in autosave after Similar Posts had hooked into the save function and since I was trying to preserve the custom field once it was saved it got messy.

    1) The duplications were in fact a way of getting MySQL to give extra weight to the most frequent terms

    2) and 3) are very valid points but they rely upon a once and for all indexing of the posts and I have tried to shift to a more dynamic model where you can experiment with different approaches to index and term extraction and the relative weights of different factors.

    The idea of a separate scheme to add or subtract terms is a possibility I will bear in mind–especially if I can find a way that doesn’t impact performance too much.

  • 172. Mark @ News Corpse  |  May 13th, 2008 at 1:16 am

    Thanks. I agree that a dynamic model has some attractive benefits. And overall, a plugin that requires no intervention from the user is the ideal. But I just think that’s fairly impossible and that the ability to fine tune results is useful.

    I had another idea: What if words in the post could be tagged so that the plugin would include/exclude them? Something like include this and exclude that

    You wouldn’t need a custom field for this and it wouldn’t be any more difficult than using italics. It could even be added to the quicktags.js.

  • 173. Mark @ News Corpse  |  May 13th, 2008 at 1:19 am

    Oops. My example didn’t display. It should have said:

    Something like include <sp+>this</sp> and exclude <sp-> that</sp>.

    I hope this shows up correctly.

  • 174. Sue  |  May 13th, 2008 at 5:14 am

    2 quick things. The first is, since the update just before this one, Similar posts is including the current post as one that is similar – to itself. In one case tonight, it presented the current post as similar to itself twice in the same post.

    The other thing is, I apologize for confusing the thumbnail issue. what I am hoping for is the ability to specify the image for Similar Posts to use if one is provided in the post. This way, the you tube videos and any other posts without images will have a thumbnail.
    many thanks,

  • 175. Rob  |  May 13th, 2008 at 10:14 am

    Mark @ News Corpse: That’s a good idea! The only catch is what happens to the added markup if — heaven forbid — you should ever abandon Similar Posts. I’ll give it some more thought. Thanks for being persistent.

  • 176. Rob  |  May 13th, 2008 at 10:15 am

    Sue: I’m looking into point one. As for point two: do you mean to supply a fallback image to use if the post lacks one?

  • 177. seat  |  May 14th, 2008 at 8:22 am

    Hello Rob,

    I have set the relative importance as follows:
    content:0 % title:100 % tags:0 %
    hoping to get exact match of post titles(which will be names of restaurants in my blog) but it doesn’t seem to work.

    I have chosen “Show nothing if no matches” but irrelevant posts are listed like in these two posts:

    While these two posts have the same titles but no “similar posts” are listed.

    I have set “treat as Chinese, Korean, or Japanese?” to yes.

  • 178. Rob  |  May 14th, 2008 at 11:23 am

    seat: Mmm food!

    Similarity is judged according to MySQL’s complicated word-based algorithm, so exact matches are always unreliable. Add in the difficulty Japanese presents to MySQL and all bets are off!

    The current attempt to work with C/J/K is very much a first try. It treats individual characters as if they were ‘words’ — a real hack. The next version which will appear soon is based on digrams which seems to get good results in the literature on similarity but, while better, is not likely to give you exact matches.

    I will be very interested to get feedback from you to make this work better.

  • 179. seat  |  May 14th, 2008 at 12:08 pm

    Thank you for the quick response. So getting an exact match is no easy feat… I look forward to the new version. Keep up the good work! :)

  • 180. fred  |  May 14th, 2008 at 8:14 pm


    Very nice plugin!

    I was having issues with it lately though, new posts wouldn’t have any related posts found, and the server logs be filled with database errors from WordPress.

    Apparently you have misplaced a closing parenthesis on line 71 when determining whether there are posts to exclude or not, and when there’s not then $exclude_posts is still set to true, resulting in a query with a ” ID NOT IN ( ) ” which of course gets an SQL error.

    $exclude_posts = (trim($options['excluded_posts'] !== ''));

    while you should have this (same as with $include_posts) :
    $exclude_posts = (trim($options['excluded_posts']) !== '');

    Thanks again for the great work!

  • 181. fred  |  May 14th, 2008 at 8:16 pm

    hmm… things got mesed in in the code block it seems.
    Anyways, here it goes again, hopefully it will work this time:
    $exclude_posts = (trim($options['excluded_posts'] !== ”));
    I think should be this:
    $exclude_posts = (trim($options['excluded_posts']) !== ”);

  • 182. Rob  |  May 14th, 2008 at 9:42 pm

    fred: You are dead right! Thanks a lot.

  • 183. Max  |  May 19th, 2008 at 6:13 pm

    Nice plugin!

  • 184. Jason Billingsley  |  May 22nd, 2008 at 8:54 pm

    We are upgrading our blog to 2.5 right now (yet to be deployed) and I must say… you are the best plugin author I have come across, hands down. You’ve thought of everything and make it so easy to make adjustments and tweaks. I’m wishing I had an extra thumb so I could give you 3 thumbs up rather than just two.


  • 185. Rob  |  May 23rd, 2008 at 10:16 am

    Jason: Many thanks!

  • 186. brad montgomery  |  May 24th, 2008 at 3:53 am

    hi there. very cool plugin. thanks so much for your efforts!

    I’m a newbie and am embarrassed to ask.

    To work this plug in, I just Install it (Had the designer do it) an then put this code IN my posts as I write.

    Is that correct?

    the new site, nearly live where we are using your stuff is here:



  • 187. Rob  |  May 24th, 2008 at 10:14 am

    brad montgomery: It looks like your code got eaten by the comment box so I can’t really say…

    It all depends where you want the similar posts listing to appear. If you want it in a regular spot on all pages of a particular kind then it is best to put it in the theme files. But if you want it appearing inside some posts and not others then you can insert the code <!--SimilarPosts--> where you wish and, as long as the option is turned on, you should see the list.

  • 188. Ionut  |  May 28th, 2008 at 6:52 am

    Hi,nice plugin, but I’m interested if I can show instead of related post titles the related posts custom field.

  • 189. Rob  |  May 28th, 2008 at 9:35 am

    Ionut: You can show ‘anything’ you want by changing the output template. The tag you probably want is {custom:fieldname}.

  • 190. David  |  May 28th, 2008 at 10:27 am

    No matches with updated similar posts plugin. I tried reinstalling without effect. Next step is working with php?????
    I guess the updated plugin is no longer working for me in that case. Too bad. It was a good one for awhile.

  • 191. VictorSP  |  May 28th, 2008 at 12:35 pm

    Hi, Rob!

    I use next output template:
    {link} – {snipet:50}

    Every post contains the same first part like this:
    “This is post about something
    #Unique part

    How I can delete not_unique part of post (“This is post…”) or any other words from snipets?

    p.s. may be something like {snipet:50;delete:”this is post”,…)

  • 192. Mikko  |  May 29th, 2008 at 5:51 am


    The plugin works fine, but my category name filter doesn’t apply to it. My filter hooks to single_cat_title, list_cats, get_category and the_category, but still the category title comes out unfiltered. Why’s that and what can I do to fix it?

  • 193. Rob  |  May 29th, 2008 at 10:45 am

    Mikko: Are you willing to try something for me? Open the post-plugin-library/output_tags.php file and find the function otf_categorynames. Replace the return $value with

    return apply_filters('the_category', $value, $ext, '');
    . You can do the same with otf_categorylinks too.

    Please let me know if that allows your category name filter to work properly.

  • 194. Rob  |  May 29th, 2008 at 10:48 am

    David: I’m glad we got that fixed.

  • 195. Mikko  |  May 29th, 2008 at 10:54 am

    Thanks, that does the trick, except that I run into problems with my filter – but that’s my problem, and I can try to solve it now.

    You see, I have names as categories, and the names are formatted “lastname, firstname”. For display purposes, I have a filter that flips them “firstname lastname”. Getting that to work with multiple categories is tricky; this is something that was much easier in Movable Type. But I’m learning here…

  • 196. Rob  |  May 29th, 2008 at 11:08 am

    VictorSP: I’ve sent you an email with a file attached for you to try.

  • 197. Rob  |  May 29th, 2008 at 11:26 am

    Mikko: It would probably be better for you if I applied single_cat_title to the individual category names. Or should I do both?

  • 198. Mikko  |  May 29th, 2008 at 11:31 am

    I switched from category names to category links (which is what I actually wanted in the first place), and that fixed things for me, everything works now as I want. As soon as I get my tags imported from MT, it’ll be interesting to see how the similarities come up – I expect an improvement, as my MT similar posts feature matched only tags. Even without the tags the results are pretty good. Thanks for the great plugin, I really like the flexibility!

    That change would probably make sense for general purposes, though.

  • 199. Heath  |  May 30th, 2008 at 4:53 am

    Rob, I’m getting the following error
    Fatal error: Call to undefined function ppl_display_status() in /home/.heebee/maland/ on line 74

    i have tried uninstalling and re-installing, deleting files from server and reuploading & and everything else I could see in this comment thread, can you give me any advice?


  • 200. Rob  |  May 30th, 2008 at 9:36 am

    Heath: My apologies — you received a development version from trunk rather than the latest stable version. The links have been fixed. Please download again and things should be OK.

  • 201. Heath  |  May 30th, 2008 at 5:31 pm

    Thanks Rob,
    I downloaded the plugin again using the link at the top of this page. I removed the old plugin through the settings screen and deleted both plugins (including library).

    I reuploaded library plugin, activated it, reuploaded similar posts plugin, activated it and got the same error.

    I then reindexed the pages and still the same error.

    i LOVE the plugin if it works, this will rock… hmmm…

  • 202. Heath  |  May 30th, 2008 at 10:06 pm

    Rob, thank you for the email!

  • 203. Robert Kingston  |  May 31st, 2008 at 12:43 pm

    Hi Heath and Rob,

    Any news back on the “/similar-posts-admin.php on line 74″ error? I’m still getting this too, after trying to re download the stable version.


  • 204. Robert Kingston  |  May 31st, 2008 at 12:45 pm

    My mistake! You need to download it from here:

  • 205. Rabie  |  May 31st, 2008 at 2:32 pm

    the same “74″ error here.. please help

  • 206. Hepsi  |  June 1st, 2008 at 2:25 am

    Hi Rob,

    Do you provide .pot .mo etc. files for other languages. Maybe I can translate to Turkish.

  • 207. Rob  |  June 1st, 2008 at 10:46 am

    Hepsi: I am working on it!

  • 208. DarkRaisin  |  June 1st, 2008 at 9:26 pm

    I have installed the latest version 2.5.0 bu tstiil get this error where erever I call similar_posts():

    You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near ‘) as score FROM `wp_similar_posts` LEFT JOIN `wp_posts` ON `pID` = `ID` WHERE ()’ at line 1]
    SELECT *, ( ) as score FROM `wp_similar_posts` LEFT JOIN `wp_posts` ON `pID` = `ID` WHERE () AND post_date <= ’2008-06-01 22:06:51′ AND post_status = ‘publish’ AND ID != -1 AND post_password =” AND (post_date <= DATE_SUB(CURDATE(), INTERVAL 0 day) OR post_status=’static’) ORDER BY score DESC LIMIT 0, 6

    I have checked the database and wp_similar_posts table is not been created. Can I created manually and what are the attribute of that table. Or can this problem be solved by other ways?

    Thanks in advance

    BTW, great job.

  • 209. Rob  |  June 1st, 2008 at 10:03 pm

    DarkRaisin: First try deactivating the plugin and then reactivating it. Then rebuild the index from the plugin’s settings screen.

    If that doesn’t work try the same process but instead of deactivating use the settings option to remove the plugin’s settings.

    If you still have no luck please submit a bug report from the settings screen as it provides me with some debugging information.

    Good luck!

  • 210. DarkRaisin  |  June 2nd, 2008 at 9:20 pm

    did all the magic you tought me but no luck, I have reported the error as you instructed.

    Thanks a lot so far.

    BTW. can I create the table my self? just tell me how many rows and culonms and waht attribute please.

  • 211. DarkRaisin  |  June 2nd, 2008 at 9:34 pm

    is this the query to create the table:

    CREATE TABLE `wp_similar_posts` (`pID` bigint( 20 ) unsigned NOT NULL , `content` longtext NOT NULL ,`title` text NOT NULL ,`tags` text NOT NULL ,FULLTEXT KEY `title` ( `title` ) ,FULLTEXT KEY `content` ( `content` ) ,FULLTEXT KEY `tags` ( `tags` )) ENGINE = MyISAM CHARSET = utf8;

    I will give it a try.

  • 212. DarkRaisin  |  June 2nd, 2008 at 9:43 pm

    yes, table created now, reindexing done. but no similar post is being shown and I am sure I have some simlar posts. :(

  • 213. Rob  |  June 3rd, 2008 at 11:34 am

    DarkRaisin: Sorry to not get back to you earlier. So you have managed to create the database and index it but still no matches are being found…

    There was something rather strange about the bug report you sent me. It should contain a list of the current settings of the plugin but yours were all blank. I do not know why this is.

    Could you send me — via another bug report — the url of your site so I can take a look at it?

  • 214. Rob  |  June 3rd, 2008 at 2:22 pm

    DarkRaisin: I think I have found the problem. Are you on a windows server? There’s a bug in your version of WordPress that stopped the installation code from running. I’ll package up a fixed version and post it later today. Please let me know if it works for your case.

  • 215. DarkRaisin  |  June 3rd, 2008 at 8:05 pm

    You are right. Server is Windows based. I am going to install version and will let you know. And I have installed Post-Plugin Library.

    Thanks again fo ryour great effort.


  • 216. DarkRaisin  |  June 3rd, 2008 at 8:15 pm

    I have removed the older version, deleted the table in database. upload and install the latest version. tried to activate; got this error:

    Fatal error: Call to undefined function ppl_plugin_basename() in D:\Domains\\wwwroot\wp-content\plugins\similar-posts\similar-posts-admin.php on line 674

    :( (

  • 217. Rob  |  June 3rd, 2008 at 9:18 pm

    DarkRaisin: Are you sure you got the latest Post-Plugin LIbrary ( ? My freshly downloaded copy has a common_functions.php file and I can see, at the bottom, ppl_plugin_basename defined.

  • 218. Annie  |  June 3rd, 2008 at 10:54 pm

    Fatal error: Call to undefined function: ppl_plugin_basename() in /home.10.13/penseeli/www/blog/wp-content/plugins/similar-posts/similar-posts-admin.php on line 674

  • 219. DarkRaisin  |  June 3rd, 2008 at 11:50 pm

    Dear Rob

    no :) mine was v. I will upgarede it tomorrow and will let you know.
    Thanks again.


  • 220. DarkRaisin  |  June 4th, 2008 at 12:01 am

    well, well. this one has created the table and indexing went also OK, but no similar post is being shown. I will try to make a bug report.

    PS: I couldn’t wait until tomorrow :)

  • 221. Rob  |  June 4th, 2008 at 12:59 am

    Version fixes, I hope, the ppl_plugin_basename problem. Don’t forget to get Post-PLugin Library too.

  • 222. Sean P. Aune  |  June 4th, 2008 at 1:06 am

    I have Post Plugin and Similar Posts and I am getting the line 674 error. Any ideas?

  • 223. Rob  |  June 4th, 2008 at 10:40 am

    If you had the misfortune to download version you may run into problems when you try to update to a newer version. I managed to introduce a circular dependence between this plugin and the Post-Plugin Library which means trying to update either from the admin plugins page will cause an error. Instead you need to delete the version from the server (Post-Plugin LIbrary too) and upload the newer one and the problem should be solved. I apologise for any worry or inconvenience.

  • 224. DarkRaisin  |  June 4th, 2008 at 10:22 pm

    Dear Rob
    I have deleted the table, older plugins, uploaded and activated v. for both plugins.
    Table has been created, indexing went also OK, but still no similar posts is being shown. I shall only use this right?

  • 225. Bee  |  June 7th, 2008 at 2:04 pm

    Thanks very much for the great plugin, Rob! I’ve tried all the other plugins I could find for this feature, and yours was by far the best after I configured the weightings.

    Now I’m looking to make use of this for the 404 page, and I have yet to find anything satisfactory. I’m currently using the Google solution but it’s too cluttered and not customisable. There’s Related Posts for 404 plugin, but I really don’t want to use the Related Posts plugin, because yours is so much better. I’ll try Tony’s solution (comment #161), but yes, I’d definitely be interested to see this feature available for Similar Posts.

  • 226. Rob  |  June 7th, 2008 at 3:40 pm

    Bee: Thanks for your kind comments! I’ll bear your request in mind. As you know my own feeling is that search engine keywords are too sparse to make for good similar matches… but I am open to persuasion.

  • 227. DarkRaisin  |  June 8th, 2008 at 10:54 pm

    Dear Rob
    Did you have time to look at my Bog-report?

    Appriciate your work


  • 228. Angelo  |  June 9th, 2008 at 10:02 pm

    Feature request! For those of us with multiple authors on our blogs, it would be really really nice to also have the author in the list, like:
    * Article by Author

  • 229. Rob  |  June 10th, 2008 at 10:11 am

    Angelo: I may be misunderstanding you… but the output tag system allows you to customise your list in many ways including displaying the post author (use the {author} tag).

  • 230. Richard  |  June 10th, 2008 at 12:10 pm

    weird dates on recent posts and similar posts. Just started getting some strange URLs on posts on Similar posts and recent comments. See my url here In the RHS panel you will see ”you may also like to read” (similar posts) checkout the list of links here, they are mixed between permalinks, 1970 dates and default URLs some links are totally wrong. See also latest 5 comments panel, and most popular. Similar faults exist I have made no hacks. All plugins are fully up to date. Please advise. Thanks.

  • 231. Rob  |  June 10th, 2008 at 12:35 pm

    Richard: Very strange indeed! Can you make a bug report … just in case it shows anything out of whack?

    Since it’s both permalinks and dates that are odd but not titles etc. it’s hard to know where the problem is. I’ll delve deeper.

    Thanks for the message.

  • 232. Richard  |  June 10th, 2008 at 2:34 pm

    Report filed. Also listed other plugins running on my site. Thanks for your attention.

  • 233. Rob  |  June 11th, 2008 at 10:00 am

    DarkRaisin: Sorry … I thought I’d replied by email.

    Your bug report shows that your Similar Posts settings are missing for some reason. You can go through the options screen and make sure that all the entries look right, saving at each screen. Alternatively, remove Similar Posts (via the settings screen), then download by hand the latest versions of the Post-Plugin Library and Similar Posts and install them.

    Let me know whether you have any joy.

  • 234. Marios Alexandrou  |  June 15th, 2008 at 2:47 am

    I’m using the latest version of the Similar Posts plug-in (v2.5.0.9). None of my posts have related posts showing. Not sure if the recent upgrade caused this problem or not, but I thought I’d mention it. I’m digging around…

  • 235. Rob  |  June 15th, 2008 at 9:58 am

    Marios: Could you submit a bug report from the Similar Posts settings screen and it might help me give me some advice?

  • 236. DarkRaisin  |  June 15th, 2008 at 10:42 pm

    Dear Rob
    Yeah, I think I misunderstood you. I have deleted the older version, installed both similar and library v. .. Now I get: None Found message.

    Here is some screens of my settings:

    General tab:
    Output tab:

    Do I need to check something in the filter tab?



  • 237. Tony  |  June 16th, 2008 at 3:51 am

    Father Marsh,
    I have sent you an email through your contact form on your blog. In that email, I have cut-and-pasted slow queries from the similar posts plugin. Perhaps you can take a look and see what you can do? Thanks!

  • 238. Rob  |  June 19th, 2008 at 3:01 pm

    DarkRaisin: I hope the next release will help you out. It should be out before very long.

  • 239. Rob  |  June 19th, 2008 at 3:07 pm

    Tony: I’ve spent quite a few hours trying to find ways of speeding up the Similar Posts queries. I tried four alternative approaches and found each to take at least twice as long. Now I am testing on a setup with only 600 posts and it may be that the different approaches scale differently since your setup seems to be much larger. So I have no easy answer for you but I will continue to look for ways to speed things up on large sites.

    If you have any suggestions I’d be very happy to hear them.

  • 240. gilda  |  June 22nd, 2008 at 1:15 am

    hello. i tried to install the similar posts plugin and have been doing that for like 2 hours but was unsuccessful. i also installed your post-plugin library, and that was ok. however, after uploading the similar posts plugin into my plugin folder, it does not even appear on my plugins list. i tried deleting and uploading again several times but nothing seems to work. do you know what i might be doing wrong?

    thank you so much.

  • 241. Rob  |  June 22nd, 2008 at 11:18 am

    gilda: I really don’t know what could be causing the problem. It should at least show on your plugins screen as a plugin to be installed–all it takes for that to happen is for WordPress to read the description at the top of the file. All can suggest is that you download a new copy of the plugin and try again.

    Please let me know if you have any luck.

  • 242. Soverato News  |  July 3rd, 2008 at 2:53 pm

    Ciao Robert,
    there be 2 things i want to suggest for this usefull plugin:
    1 – tag rel = nofollow for the link
    2 – alt tag with the post title


  • 243. Rob  |  July 4th, 2008 at 10:36 am

    Soverato News: Thank you for your interest.

    Both of those possibilities are available now. In place of the {link} output tag you can ‘build your own’, e.g.:

    <a href="{url}" alt="{title}" rel="nofollow">{title}</a>

  • 244. Soverato News  |  July 4th, 2008 at 12:25 pm

    thank you very much for quick replay tutorial :-) .


  • 245. crystalline  |  July 6th, 2008 at 11:03 pm


    i’ve been unable to get the related posts plugin to work, but the recent posts and recent comments do, which is confusing. they all show up in plugins and i can change the options.

    i’ve basically got the same code repeated three times to embed recent posts, related posts, and recent comments into the sidebar, but the related posts part seems to just be skipped over, and it doesn’t create the section in the sidebar at all. any ideas what could be causing that?

  • 246. Rob  |  July 7th, 2008 at 9:30 am

    crystalline: If I could see the code it might help. If you post it here don’t forget to enclose it in <code> .. </code>

  • 247. crystalline  |  July 8th, 2008 at 2:06 am

    okay, this is what i have:

    <div class="posts">
    		<ul id="recentposts">
    			<li id="recent-posts">
    			<h2>Recent Posts</h2>
    					<?php recent_posts(); ?>
    	<div class="similar_posts">
    		<ul id="similarposts">
    			<li id="similar-posts">
    			<h2>Related Posts</h2>
    					<?php similar_posts(); ?>
    	<div class="recent_comments">
    		<ul id="recentcomments">
    			<li id="recent-comments">
    			<h2>Recent Comments</h2>
    					<?php recent_comments(); ?>

    i’m confused, because the similar posts part doesn’t seem to display anything, but the recent posts and recent comments both work. all 3 of the plugins show up as activated in the wp admin section, and i can change options and whatnot…

  • 248. crystalline  |  July 8th, 2008 at 2:34 am

    well, um…

    it just… started working. and i didn’t change anything relevant that could’ve fixed it. which kinda bothers me, because now i don’t understand what was broken or why it now works, haha.

    now that i’m here, here’s another one: how do you get the little mini “document” icon that appear sto the left of the similar posts? they are there for recent posts and recent comments.

    thanks :)

  • 249. Rob  |  July 10th, 2008 at 10:36 am

    crystalline: I’m glad it came to life for you!

    The icon is part of the theme I use — automatically applied to sidebar list items as a background image I believe. The icon set used is by Kevin Potts.

  • 250. Tanner  |  July 11th, 2008 at 3:41 am

    Absolutely excellent plugin. It installed with no problems and is working great in FF3. Many thanks!

  • 251. ScoopCelebrity  |  July 14th, 2008 at 3:23 pm

    I post you bug report through form, but I found the problem with upgrade to version.

    Settings change after upgrade and field “Display posts that are:” – “Published” is set to “NO”. That is the problem I couldn’t see any Similar Post.

    My regards, ScoopCelebrity

  • 252. Arvind  |  July 14th, 2008 at 6:19 pm

    I upgraded both post-plugin, and similar posts.
    strange is that I see both No Related Posts, and Similar posts, both printed. Have I missed any thing ?
    Related posts

    * No related posts.

    * Travel from Boston to Bangalore
    * 1947 -> 2007
    * science identifies risks…

  • 253. Rob  |  July 14th, 2008 at 9:53 pm

    ScoopCelebrity: Thanks for the message. Can you tell me the version you upgraded from?

  • 254. Rob  |  July 14th, 2008 at 9:55 pm

    Arvind: Looking at the source of your web page in my browser I can see that Similar Posts is being called two times. Is that deliberate?

  • 255. Arvind  |  July 15th, 2008 at 3:48 am

    I looked at single.php, I have invoked it only once. Thats’ my intention too.
    Is it possible to figure out where else it may be hiding ?

  • 256. Rob  |  July 15th, 2008 at 11:28 am

    Arvind: The page source has the two appearances separated by some html. After the first list there are two closing divs one for the post and one for the entry. The second list is prefixed by an opening entry div which never seems to be closed.

    Very strange. Would you be willing to send me the php file by email? I’ll drop you a note with my address.

  • 257. baron  |  July 16th, 2008 at 4:19 pm

    hi. Thanks for plugin



  • 258. Vikram  |  July 17th, 2008 at 1:11 am

    I am using WordPress MU (1.5.1).

    After adding and activating the plugin (and the post plugin), I can’t seem to get Similar Posts to work. The output says similar posts took these many seconds, but there is no output.

    I checked the database, and there is no wp_similar_posts table. I go no errors when activating the plugins. I can go the administration page, and then set the configuration items, and they seem to change (for example, show 2 posts instead of 5). These configuration items were all set to empty when I got in there the first time.

    Any ideas? It affects all the blogs in this network using WordPress MU.


  • 259. Amit  |  July 17th, 2008 at 10:03 am

    I tried to installed the plugin but i am getting the “none found” whatever i try.

    i have wordpress 2.5.1 installed and i have installed the 2.6.0 similar post plugin alongwith the post plugin library from your site.i tried to configure the settings but all in vain.i also run the SQL query successfully that you have provided un FAQ no1.

    Please guide me how to set it up in my blog.feeling very frustrated

    many thanks


  • 260. Rob  |  July 17th, 2008 at 10:50 am

    Everyone: This sudden flurry of installation problems are presumably all related. I haven’t tracked down the cause yet but you could all help me by sending in a bug report from the plugin’s settings screen. I might be able to see a common pattern.

    Thanks for your patience and help.

  • 261. Rob  |  July 17th, 2008 at 5:11 pm

    NB: I believe I have found the cause of the installation problems — related to WP 2.6′s capacity to relocate the content folder — and, if I am right, version should fix things.

  • 262. Anfi  |  July 20th, 2008 at 7:25 am

    Good plugin! Senks =)

  • 263. Amy  |  July 22nd, 2008 at 8:36 am

    Plugin is down??

  • 264. Rob  |  July 22nd, 2008 at 10:44 am

    Amy: It seems to be working OK — the plugin is hosted with WordPress Extend and their uptime is usually pretty good.

  • 265. Enrico  |  July 25th, 2008 at 10:57 am

    I was trying to match posts just by giving all weight to the title and 0 to tags and posts. But somehow words that have 2 or 3 characters are taking into account by trying to find matches. Is there any way to apply the same rules like for the post content. Adding the words to the variable $tinywords did not change anything. Thank you very much for your help.

  • 266. Stephen  |  July 26th, 2008 at 2:48 pm

    I use it on my blog. One of my favorite plugin. Mahalo.

  • 267. Tony  |  July 26th, 2008 at 6:08 pm

    Hi Fr. Marsh.

    I’m getting some strange messages in my error_log file.


  • 268. Tony  |  July 26th, 2008 at 6:10 pm

    Wow. What was that? I’ll just email them to you.

  • 269. Rob  |  July 26th, 2008 at 8:21 pm

    Tony: Thanks. I can see the problem and it’s easy to put right.

  • 270. Thomas Böcker  |  July 26th, 2008 at 10:35 pm

    I have a problem since I upgraded to WP 2.6
    Similiar Posts is installed with the newest version but I get this error you can see on this picture:

  • 271. Rob  |  July 26th, 2008 at 10:54 pm

    Thomas Böcker: Can you submit a bug report from the plugin’s settings screen? That will let me know the options you have set.

  • 272. Thomas Böcker  |  July 28th, 2008 at 10:41 am

    Hey Rob, I just mailed you the requested bug report ;)

  • 273. Dresah  |  July 30th, 2008 at 7:15 am

    Is it compatible with 2.6?

  • 274. Rob  |  July 30th, 2008 at 4:34 pm

    Dresah: Yes, as it says at the top of this page, the latest version of the plugin is compatible with WordPress 2.6

  • 275. kompass  |  July 31st, 2008 at 9:20 am

    useful plug-in! but what about russian lang?

  • 276. Rob  |  August 1st, 2008 at 2:21 pm

    kompass: If your site is using the utf-8 character set and you set the plugin index to use extended characters Similar Posts should work with Russian text. There is no supplied stop-word list or stemmer though — if you can add them it will probably improve accuracy somewhat. (and if you do I will be glad to include them in the package)

  • 277. Scyfox  |  August 3rd, 2008 at 12:51 am


    I Recently posted a bug in the admin area , output tab.

    this error apears. Fatal error: Call to undefined function ppl_display_trim_before() in /home/.lolli/scyfox/ on line 115

    The plugin still works but dunno what is causing this.

    One other thing. There’s any way I can use the function_exist() function to check if the plugin is active show the content or else… cause I tried with this and didn’t work

    <?php if(function_exists('similar_posts()')){

    I place the original code and worked like wonder, but it would be really nice that in case of deactivating the plug it doesn’t break the template.

    Just a thought

    Best of luck


    Best of luck

  • 278. Rob  |  August 3rd, 2008 at 10:52 am

    Scyfox: Just a typo I guess… function_exists uses the name of the function so you should not include the parentheses.

  • 279. Open Alternatives  |  August 3rd, 2008 at 1:17 pm

    Hi ,

    We are trying to download this plugin but it gives 404 error. We tried from wordpress as well as this website. Please help.

  • 280. Marde  |  August 3rd, 2008 at 4:39 pm

    I also get a “file not found” error when I try to download version

  • 281. Rob  |  August 3rd, 2008 at 9:19 pm

    The plug-in is hosted at the WordPress Extend repository. It is downloading fine for me whenever I check it out…

  • 282. The Doctor What  |  August 6th, 2008 at 6:38 am

    Minor typo in similar-posts.php:


    (one occurance)

    Found with: define(‘WP_DEBUG’, true);

  • 283. Rob  |  August 6th, 2008 at 3:39 pm

    The Doctor What: Thanks! That’s quite an important typo! It’ll be fixed in the next release.

  • 284. DarkRaisin  |  August 6th, 2008 at 11:06 pm

    Hi Bob
    I am still getting none found. I have removed the older versions installed and activated both library and similar, reindexed the database but still getting no similar posts. the tilte of posta re in English though and have some 6000 posts. I am sure there are some similar post title in my database,
    Any help would be approciated.


  • 285. Rob  |  August 7th, 2008 at 11:15 am

    DarkRaisin: We really need to solve this!!! Can you please send me another bug report from the Similar Posts settings screen and we’ll start from there. Thanks!

  • 286. tuga  |  August 9th, 2008 at 5:06 pm

    file not found….

  • 287. Emrecan  |  August 11th, 2008 at 10:39 am

    i installed it thank u

  • 288. DarkRaisin  |  August 12th, 2008 at 1:51 am

    I was not able to submt a bug report, it gives an error everytime:

    Error 403
    We’re sorry, but we could not fulfill your request for /report-a-bug/ on this server.

    You do not have permission to access this server. Data may not be posted from offsite forms.

    Your technical support key is: 5ab8-7e8d-cd36-1abb

    You can use this key to fix this problem yourself.

    If you are unable to fix the problem yourself, please contact rmarshsj at and be sure to provide the technical support key shown above.

    Any help?


  • 289. Carlos  |  August 12th, 2008 at 4:09 am

    Download link seems to be broken?

  • 290. Rob  |  August 12th, 2008 at 9:24 am

    DarkRaisin: I have traced the problem with bug reporting to the latest version of the Bad Behavior anti-spam plugin. I’ve deactivated BB while I look for a workaround so you should once again be able to report bugs from the settings screen.

  • 291. Rob  |  August 12th, 2008 at 9:35 am

    Carlos: Can you tell me what the link is that seems to be failing?

    I think the problem is due to some intermittent trouble with the servers but it would be good to make sure that is the link you are talking about.

  • 292. Helena  |  August 12th, 2008 at 11:04 pm

    Hi, I’m trying to show similar post after a single post based on Match the current post’s tag. I have only one. I have sett Number of posts to show to 30. I have 21 posts that I want to display but only 15 come up. Any Ideas what’s wrong?

  • 293. Eco Blog  |  August 13th, 2008 at 4:23 am

    thanks for the great plugin

  • 294. Rob  |  August 13th, 2008 at 3:07 pm

    Helena: It may not actually be wrong, strange as it may seem. Similar Posts uses the MySQL full text search facility to query the database and it only returns posts it considers similar in some way. It sounds like you have 6 posts which MySQL is ignoring as too unlike to consider.

  • 295. Helena  |  August 15th, 2008 at 11:22 pm


    I’m only interested of matching by tags, so I have sett “Other Settings→Relative importance of:” to content 0%, title%, 100% tags. Are there any other settings that might be of importance? Or maybe I should do this with manual links in custom field. But I don’t understand how to configure it. Sorry.

    Also I only want to show 1 category name in the output. (I use several categories like tasted, brewage, beer and drink…for layout on index page category etc.) I only want do display beer or red wine if it’s wine. I have bee trying with something like this:
    $os = array({categorynames: , });
    if (in_array(“Vitt vin”, $os)) {
    echo “Vitt vin”;
    if (in_array(“Rött vin”, $os)) {
    echo “Rött vin”;
    if (in_array(“Mousserande vin”, $os)) {
    echo “Mousserande vin”;
    if (in_array(“Öl”, $os)) {
    echo “Öl”;
    I don’t know if this is to much to ask, but please help.

  • 296. Helena  |  August 15th, 2008 at 11:23 pm


    I’m only interested of matching by tags, so I have sett “Other Settings→Relative importance of:” to content 0%, title%, 100% tags. Are there any other settings that might be of importance? Or maybe I should do this with manual links in custom field. But I don’t understand how to configure it. Sorry.

    Also I only want to show 1 category name in the output. (I use several categories like tasted, brewage, beer and drink…for layout on index page category etc.) I only want do display beer or red wine if it’s wine. I have bee trying post the code but it dosen’t work.
    I don’t know if this is to much to ask, but please help.

  • 297. Helena  |  August 15th, 2008 at 11:27 pm

    I’m so Sorry for the duplicated entries. I got error messages when I posted the comment. Sorry //Helena

  • 298. Rob  |  August 16th, 2008 at 10:36 am

    Helena: No problem. My ISP has been fiddling with security settings and I’ve been getting strange events like that. I hope it will settle down soon.

    Let me ponder on your question for a little while to see if there’s a simple solution. OK?

  • 299. Rob  |  August 16th, 2008 at 3:07 pm

    Helena: The first part of your question is about how to set up Similar Posts to just match on tags. In addition to biasing the matching algorithm the way you have done you could also set the plugin to match the current post’s tags. In fact, if you are just matching on tags you might find you can use the simpler Recent Posts plugin (with the match tags option) to get your list of related posts. If you don’t like the age-bias of Recent Posts you could go for Random Posts. Similar Posts will work fine — just giving you some other options.

    Now for your other (harder) question. The following bit of code should do it.

    if (in_array('Vitt vin', $os)) echo 'Vitt vin';
    else if (in_array('Rött vin', $os)) echo 'Rött vin';
    else echo 'other';

    Your own code had some non-standard quotation marks which would crash it. Give it a try and let me know how it goes.

  • 300. DarkRaisin  |  August 16th, 2008 at 10:22 pm

    I am writing this comment to show my appriciation – which is nothing in compare with what you have done- .

    Thanks for your great plugin and outstanding support. The plugin works now even for me with my ancient WP, as you nicely put it.

    Thanks again


  • 301. DarkRaisin  |  August 16th, 2008 at 10:29 pm

    Just one more thing, is this plugin case sensitive?

  • 302. Rob  |  August 17th, 2008 at 10:28 pm

    DarkRaisin: Than you very much!

    The match is done without case-sensitivity because the underlying fulltext search is case-insensitive.

  • 303. Helena  |  August 19th, 2008 at 11:53 pm

    Hi, thank you so much!!! You are my hero. The code works just fine. It’s funny but suddenly
    my list of 21 posts appears but I lost one post from a list of five. (I don’t know if it ever was there, I just noticed it). But I have been adding the tags once more. I will check out the other plugs that you suggests. The output looks really nice now. I’m linking tasting notes/score to a main article. So I hope the plugs you suggest are as refined as you plug. ;-)

  • 304. Rob  |  August 20th, 2008 at 2:03 pm

    Helena: I’m glad it’s working properly at last. Random Posts and Recent Posts are also my plugins and have the same set of options so you could just slot them in instead.

  • 305. Gero  |  August 21st, 2008 at 11:13 am

    Also the German stemmer.php is not UTF-8 encoded and is causing a crash when saving/autosaving a post. Converting it from WIN-ANSI to UTF8 will fix this.

  • 306. Rob  |  August 21st, 2008 at 3:24 pm

    Gero: Thanks! Similar Posts corrects the problem.

  • 307. Robert@PNG  |  August 24th, 2008 at 4:21 am

    After a bit of fiddling I have managed to get similar posts template tag working after modifying the loop and creating some basic CSS.

    Just to let you know that previous to this plugin I was using the equivalent function available through the Simple Tags plugin and wanted to let you know that what ever algorithm you have implemented to select similar posts – it’s absolutely magic!!

    The similarity of posts now displayed since moving to your plugin is unbelievable.



  • 308. Rob  |  August 24th, 2008 at 8:28 am

    Robert@PNG: I’m very glad to hear that Similar Posts is up and working well for you!

    After replying to your comment yesterday I found myself wading into creating the code necessary to do automatic placement of similar post lists. Easy at first … and then I got into refactoring code to make it shareable between the four post plugins … and fixing interactions with the in-post placement code … and making sure that excerpts and snippets don’t generate infinite loops as they append themselves to themselves… A lot of fun! I think the result will a big improvement on several fronts … once I get the other half of the code sorted out.

    So, thank you (I think!).

  • 309. meehawl  |  August 26th, 2008 at 6:26 am

    I have an odd problem. I just installed Similar Posts and Post Plugin on WP 2.6.1. I get some similar posts but, using both the {link} and an explicit {title} it seems as if all the links for each item found point back to the originating page URL. Demo page with this behaviour linked to in the URL field for this post, or check this:

    Thanks for any help.

  • 310. Rob  |  August 26th, 2008 at 8:53 am

    meehawl: That is indeed odd. Looking at your page;s source I wonder if it is because the Similar Posts listing comes before the post loop? If it does it might account for the strange behaviour — the plugin has to know which post is being displayed so that it can look for something related.

    I may be wrong — your theme may be doing something clever — but you would have to change the order of the code so that the similar posts plugin comes after the ‘loop’.

    Make sense?

  • 311. meehawl  |  August 27th, 2008 at 6:26 am

    Thanks, that was it. When I move the Similar Posts widget to sidebar \”2\”, executing on the rhs of the page it works, presumably ensuring that it executes after the loop.

  • 312. Phoenix  |  September 1st, 2008 at 6:30 am

    Hi, first i want to say thank you for this plugin. It’s easy to use. Can i use this on 404 page? I mean, if someone looking for something and land on the 404 page, they will found related post with what they looking for. How/what code i need to put on my 404.php. Hope you understand my question:)(sorry for my English).

  • 313. Rob  |  September 1st, 2008 at 8:04 am

    Phoenix: You could use Similar Posts to do this kind of thing but so far I’ve advised people requesting it that it is probably better to use search rather than relatedness. The reason is that the similarity algorithm is designed to use (relatively) large blocks of text from a post, title etc. to make the match but on a 404 page you would only have a few words to play with and a search would, I believe, give better results.

    However, I get lots of requests for this so maybe I should actually try it out and see what happens…

  • 314. Phoenix  |  September 1st, 2008 at 11:21 am

    Thanks for the quick reply:). Well i guest i have to optimize my 404 page in different way. Thanks again..

  • 315. Hayley  |  September 2nd, 2008 at 10:58 pm

    Sorry im blonde and confused. Which file do i have to edit so it shows on my main page and a single post? im rubbish at html im only used to installing easy plugins but the ‘yarp’ plugin didnt work for my version.

  • 316. Rob  |  September 3rd, 2008 at 8:17 am

    Hayley: Can you wait for a day or two? The next release of Similar Posts will have automatic placement.

    Otherwise you will need to edit two files in your theme. If you want to have a list right after the single post’s content open single.php and add the following line after the line where ‘the_content’ is output:

    <?php if ( function_exists('similar_posts') ) similar_posts(); ?>

    You can do a similar thing with the index.php file to display the list after each post on the main page.

  • 317. Mexico SEO  |  September 3rd, 2008 at 11:06 pm

    Very flexible and customizable, a lot of upgrades, congrats for your great job !

  • 318. Hayley  |  September 3rd, 2008 at 11:38 pm

    I can wait for the next release then, as i dont really understand editing files.

    Thank you :)

  • 319. Axel Dittmann  |  September 8th, 2008 at 12:58 pm

    PLEEEASE HELP ME! What is wrong with the following code:

    {php:$thumb=get_post_meta($result->ID, \'image\', true);if ($thumb)echo img src=\"$thumb&h=60&w=60&zc=1&q=80\" alt=\"test\" align=\"right\";}

  • 320. Rob  |  September 8th, 2008 at 2:29 pm

    Axel: Nice site!

    It is hard to tell in the abstract what is wrong — there are a couple of things that might be wrong. Does the template produce any output? If so what?

    First I don’t think you should need to escape the quotes. Second I think the string being echoed should be quoted. Third there seems to be missing angle brackets (though they may be just not shown here).

    My usual tactic forming {php} ouput template tags is to make sure the PHP runs correctly if inserted directly into the template file. You may have to fill in certain values (like $result->ID) but it helps catch any errors.

  • 321. CWFGameCast  |  September 9th, 2008 at 2:29 am

    I know previous versions of this and the Post-Plugin Library had problems using the automatic upgrade included with WordPress. Has this been fixed yet and if not when can we expect that to happen?

    I don\’t mind doing upgrades the old fashioned way but being able to do it automatically for all my other plugins but not this is a major pain.

  • 322. Rob  |  September 9th, 2008 at 8:28 am

    CWFGameCast: The upgrade issue affected a couple of releases a few months ago and has been fixed since. Are you still having problems?

  • 323. proslaviy  |  September 16th, 2008 at 2:01 pm

    Hi, how I can send PM?

  • 324. Rob  |  September 16th, 2008 at 2:52 pm

    proslaviy: I have no idea what you mean, sorry.

  • 325. Ian  |  September 24th, 2008 at 7:56 pm

    Hi Rob,

    I’m trying to use Similar Posts to display images that I’ve entered in the Excerpt field of the Write Post page.

    However, using the {excerpt} tag when configuring the Output options just generates an empty list in my similar post section.

    If I change the tag to some text, the output is displayed as expected.

    Does this mean that I simply can’t use {excerpt} to display images in the Excerpt field or is there some work around I can use?


  • 326. Rob  |  September 25th, 2008 at 8:35 am

    Ian: The {excerpt} output tag has a number of options. the first version I wrote a long time ago didn’t properly pay attention to pre-existing excerpts but if you use the ‘b’ parameter a rather better algorithm does, e.g.,


    or, if you are happy with the default number of words, just use,


    I haven’t tried this with images in the excerpt but can’t see why they shouldn’t work. Let me know.

  • 327. Ian  |  September 25th, 2008 at 9:17 am

    Hi Rob,

    That’s brilliant!

    Using the default number of words option:


    has worked perfectly with images.

    Thanks so much for this Rob, you make my (WordPress) life so much easier :)

  • 328. dazz  |  September 26th, 2008 at 3:59 pm

    I’ve got a problem with Similar Posts: it overrides the settings of another plugin “All in one SEO Pack”. All In One SEO Pack rewrites the title of each posts like “post title” | “blog title” but since the latest version of Similar Post it only shows “Blog title” everywere as the page title. Any clues how I can resolve this?

  • 329. Rob  |  September 26th, 2008 at 5:39 pm

    dazz:Can you be more specific about how to reproduce the problem? I have both plugins installed on my test system and they seem to be cohabiting amicably.

  • 330. dazz  |  September 26th, 2008 at 5:45 pm

    Ok, I’ll do my best to explain myself. All In One has a feature to optimize pages by rewriting the titles of the pages ( the tags) and conveting the titles to | . Well, without Similar posts activated, that works perfect. But when Similar posts is active, all the pages, all the posts pages of my blog have as title. This bug is new, as it didn’t happened with other versions of SP.

  • 331. Rob  |  September 26th, 2008 at 9:05 pm

    dazz: What I was trying to say was that All in One SEO is working properly alongside Similar Posts on my test site. There must be some difference between your setup and mine and that difference we need to find out in order to understand your problem.

  • 332. dazz  |  September 26th, 2008 at 9:12 pm

    In All In One SEO Pack’s config do you have rewrite titles enabled?
    Besides thatI have the default configuration’s value for both of the plugins.

  • 333. Rob  |  September 26th, 2008 at 10:47 pm

    dazz: Yes I do and it works fine with Similar Posts active.

  • 334. Kalle Kniivilä  |  October 5th, 2008 at 7:38 pm

    I really enjoy the plugin, I just installed it last night, and it is working great on my site However, there is a small issue that seems to be related to the plugin, as I can’t recall this happening (much) before I installed the plugin, but now it is happening all the time: when creating or editing a new post, I get a totally blank page after pressing the “save” or “publish” buttons. The post is saved fine, however. Any idea why this is happening? I’m just guessing, but maybe the data base is responding too slowly to some request the plugin is making when saving the post?

  • 335. Rob  |  October 6th, 2008 at 8:46 am

    Kalle Kniivilä: That’s an odd one! I haven’t heard of this issue before. One thing you could check is whether increasing the memory limit for PHP makes a difference. WordPress 2.5+ tries to increase the memory to 32M but5 you can increase that by putting

    define('WP_MEMORY_LIMIT', '64M');

    into your config.php file. Or you could do it in a php.ini file.

    Also, if you have access to your PHP error logs that may shed some light on what is happening with the blank page.

  • 336. Kalle Kniivilä  |  October 6th, 2008 at 9:26 am

    I added the memory limit code at the end ov my wp-config.php file, but that didn’t seem to change anything. Is that the right place for it? I think it was parsed, anyway, because first I happened to place it after the PHP end code, and the line turned up at the top of my page. :-)

    I had a look at the PHPMyAdmin interface, but really couldn’t make out where I should look for the error log.

  • 337. Kalle Kniivilä  |  October 7th, 2008 at 2:07 pm

    I have an error log file for the blank page, it includes items like tthis:

    Notice: Undefined index: wp_cron_daily in /customers/ on line 583

    and a lot of

    Notice: Undefined property: stdClass::$args in /customers/ on line 1066

    and then

    Warning: Cannot modify header information – headers already sent by (output started at /customers/ in /customers/ on line 689

    Any idea what this is? I can’t see anything directly related to your plugin, but everything worked OK before I installed it. And last night, when I uninstalled your plugin and then reinstalled it, everyghing worked fine. But when I posted a new text today, I got the blank page thing again…

  • 338. AlexG  |  October 9th, 2008 at 11:52 am

    You asked in the post 276. Here they are.

    # Russian stopwords, charset koi8-r
    #Charset: koi8-r
    #Language: ru


  • 339. ocj  |  October 12th, 2008 at 12:13 am

    I am using both, the Similar Posts-Plugin and the WP-Footnotes-Plugin ( The Similar Posts-snipplet is currently placed above the Footnotes-snippet on the single page view.

    Is there any way to change this order, so that the footnotes appear above the Similar Posts snippet?

  • 340. Carly  |  October 13th, 2008 at 7:26 pm

    Daz – What you could possibly do is edit your themes header.php file and manually add your sites name in the title ie something like:

    <?php wp_title(); ?> |

    Then just omit that from your AIOSEO settings.

    Rob – Firstly thanks for the great plugin, it’s the best related post plugin out there.

    What i’m wondering, is there anyway to optimize it for very large sites by creating other indexes in the database or something similar?

    In the database i have

    Data 161.2MB
    Index 323.5MB
    Total 485.6MB

    So the site is pushing almost half a Gig in the wp_similar_posts table. So any tips on optimizing things for such data?

    Thanks Rob.

  • 341. demetris  |  October 18th, 2008 at 6:07 pm


    I’m having an HTML validation problem that may be related to Similar Posts. When I enable “Output after post”, a single, extra closing paragraph tag appears in the source after the “Similar Posts took…” comment, preventing validation.

    Is anyone else seeing this?

    Thanks for the great plugins,

  • 342. photoTristan  |  October 18th, 2008 at 10:56 pm

    Great plugin!

    I had been looking for a related posts plugin that didn’t require me to have to edit scary PHP files. I’m glad I found this one.

    I’ve implemented it on my site now and it seems to be working well.

  • 343. mascali  |  October 19th, 2008 at 6:09 am

    One on the best WP plugins, seriously.
    Many thanks and greetings from Italy

  • 344. Chris  |  October 19th, 2008 at 11:34 am

    Have now the ‘none found’ message for the last 2 days.

    I didn’t change anything, no new plugins, no settings changed. Just published another post as the only activity during the last week.

    Now I have the ‘None Found’ Message again (see right sidebar of my site).

    Tried to rebuild the index, ease the setting restrictions, but no avail.

    Unfortunately I don’t know where to put in the table command (php SQL), but the table should be there, as it worked before.

    Latest Version and for the Post Plugin Library.

    Great plugin, so far no problems, but now.

    What else can I try? Thanks for your help!


  • 345. photoTristan  |  October 19th, 2008 at 6:53 pm

    Is there a way to disable similar posts on a per post basis? I’m not clear on how to do this.

  • 346. Doug  |  October 26th, 2008 at 4:19 am

    Is there a way to make this display horizonal instead of vertical.. I am useing all thumbnails want them sideways. It seems that by default the first related post in the list is give the UL value so it screws up.. Is there a way to get around this? also my “add a comment” box is bleeding getting pulled up onto the same line as the list. Thanks

  • 347. rudiger  |  October 27th, 2008 at 9:20 am

    Hi, thanks for Your plugin Similar Posts. It ‘s very usefull. I have the following question about omproving the plugin while matching categories:

    In use Similar posts in my wordpress-blogg, where all posts are getting multiple categories. Let’s name the categories for example “A”, “B”, “C”and “X”.

    Now I want the plugin to list similar posts matching any of the categories “A”, “B” or “C”. The category “X” should be ignored. That means: I don’t want to exclude the posts only because they are in category “X”. I just want the plugin to ignore the category “X”.

    This would give for example the following results:

    Take two posts. The first one gets the categories “A + X”, the second one “B + X”. With this combination the plugin should identify the two posts are not similar.

    Now take two other posts. The first one gets the categories “A + B + X” and the second post “A + C + X”. Given this combination I wish the plugin to identify both posts are similar, despite category “X” is excluded in the plugin.

    My question: Is it possible to ignore certain categories in this way? What do I have to do, to set up the plugin?

    Sorry for my English. With kind regards,

  • 348. Javier  |  November 5th, 2008 at 12:16 am

    Hi Robert:

    Does this plugin a cache system?


  • 349. Georgy  |  November 6th, 2008 at 4:17 pm

    Thanks ….very useful plugin…

  • 350. scampage  |  November 11th, 2008 at 12:43 pm

    thanks for this info..

  • 351. mike  |  November 18th, 2008 at 10:09 pm

    thanks. i’v been looking for something like this to add to some of my blogs.

  • 352. Jason  |  November 22nd, 2008 at 2:29 am

    HI, I started using similar posts WP plugin. I think I installed it a long time ago, but I never added the: anywhere, and it worked fine, however now I want to move it, and I can’t find the: code. I’ve changed templated, etc. Did I put this in one of the ‘core’ wordpress php files? If so, where would I look now to find it. Any suggestions would be great.

  • 353. Mark  |  November 30th, 2008 at 4:05 am

    This plugin doesnt seem to work with WordPress 2.6.5:

    Plugin could not be activated because it triggered a fatal error.

    Warning: require_once(/home/mysite/public_html/wp-content/plugins/similar-posts/languages/en/stemmer.php) [function.require-once]: failed to open stream: No such file or directory in /home/mysite/public_html/wp-content/plugins/similar-posts/similar-posts.php on line 569

    Fatal error: require_once() [function.require]: Failed opening required ‘/home/mysite/public_html/wp-content/plugins/similar-posts/languages/en/stemmer.php’ (include_path=’.:/usr/lib/php:/usr/local/lib/php’) in /home/mysite/public_html/wp-content/plugins/similar-posts/similar-posts.php on line 569

  • 354. Mik  |  December 4th, 2008 at 12:47 am

    Like the plugin, is there anyway for later releases to add the option to add nofollow or follow tags onto the similar posts links?

  • 355. Keral Patel  |  December 7th, 2008 at 6:24 am

    Don’t know why but it is showing me error that it cannot load the page.

    I am using the latest version of wordpress right now.

  • 356. Jak  |  December 9th, 2008 at 2:15 am

    Thank you for your software

  • 357. Dan  |  December 9th, 2008 at 9:07 am

    Still have the error:
    Fatal error: Call to undefined function ppl_display_limit() in /home/sites/ on line 70

    I tried several versions, new and older, and it still there.

  • 358. Alex  |  December 12th, 2008 at 8:14 am

    Q: Supported WP 2.7?..

  • 359. max  |  December 14th, 2008 at 7:35 am

    Does this work with wordpress 1.5.2? I have installed it and it does not seem to be working ?

  • 360. markus  |  December 18th, 2008 at 9:23 am

    when i change the $default_output_template=’..
    in similar-posts.php it dont have any effect on my website.. it still shows the {link] version, but i saved it correctly..

    i dont get it, i thought its a dreamweaver problem, but i downloaded the file on my local pc via ftp and there is nothing like {link} in the file.

    i refreshed my browser correctly.. any clue for me?

  • 361. markus  |  December 18th, 2008 at 9:30 am

    ok i got it, i had to change it wp-admin
    my fault

  • 362. Chris  |  December 18th, 2008 at 6:09 pm

    Seems the Plugins are discontinued? There isn’t any feedback since early October and I have more problems than ever with WordPress 2.6.2 and 2.7.

    Always the same Similar Posts are shown and for Recent Posts and Recent Comments I can’t access the options pages anymore. (“Cannot load recent-posts.php” error and “Fatal error: Cannot redeclare recent_comments() (previously declared in …” error).

    What to do? Ahhhhh, Rob, come back please! ;-)

  • 363. Rick  |  December 19th, 2008 at 9:11 am

    does it support thumbnail?

  • 364. Miguel  |  December 20th, 2008 at 4:54 am

    Rob nevermind…. im good!! u can delete my comment if u want

  • 365. Widge  |  December 25th, 2008 at 10:40 am

    I’d like to add my voice to those looking to exclude certain terms from being used to match posts.

    In my case, I have a certain category in which I credit Hollywood Reporter and Variety as sources quite often. Because I do this, I’m sure those three words rank high in that category for matching–and as a result, they all tend to be similar to each other and only to each other because of those words.

    If I could just remove those three words from the equation, my similar posts showing up in that category would be a lot more relevant.

    Other than that, the thing’s been running like a caffeinated fever dream–my favorite kind. Thanks!

  • 366. Leigh  |  December 27th, 2008 at 10:19 am

    I’m using WordPress as a CMS, and don’t want to use the word ‘posts’ in the heading.

    How can I change it from ‘Similar Posts’ to, eg ‘Related Articles’?

  • 367. Halycon Prime  |  January 11th, 2009 at 8:40 am

    I have it set to go by tags, but not exact and it is showing NONE FOUND for two posts that ought to be showing each other.

  • 368. African Safari  |  January 14th, 2009 at 9:25 am

    i have been looking for this plugin for my African safari and travel website. Thanks

  • 369. halgerd  |  January 15th, 2009 at 10:43 am

    Does not work in WP 2.7

  • 370. Robert@PNG  |  January 15th, 2009 at 11:34 am

    Yes it does!
    (On my blog anyway – and I run it along side about 60 other plugins)


  • 371. Johan  |  January 17th, 2009 at 8:57 am

    I also have problems with similar-posts on WordPress 2.7 (excerpt doesn’t work), but it seems related to the the_excerpt() function template-function, which doesn’t work anymore on my site.
    Maybe it has something to do with other plugins, but I will keep looking into it, because simalar-posts is a very nice and especially configurable plugin !

  • 372. Skidka  |  January 22nd, 2009 at 2:36 pm

    It works well for me, thanks!

  • 373. Jeff R.  |  January 30th, 2009 at 6:39 am

    It’s thank a plugin developer day at WordPress…so…

    I wanted to give the developer of this similar posts plugin a big thank you. This plugin has been accurate in identifying similar posts and has greatly increase the length at which my users hand out at my blog and explore.

    We appreciate your hard work.

  • 374. Tanguillo  |  January 30th, 2009 at 3:51 pm

    Yes indeed Robert! You are an example to al plugins developers. Not only you have amazing plugins, but your support response was always incredible fast.
    Thank you very much!!!

  • 375. Garden  |  February 7th, 2009 at 6:51 pm

    Thanks for this great plugin.. work like charm.

  • 376. izac  |  February 7th, 2009 at 11:09 pm

    great plugin thx for that !

  • 377. Dimi  |  February 16th, 2009 at 11:16 pm

    When I try the custom field {custom:thumbnail} to pull thumbnails it returns the location URL of the image instead of the image itself.
    What is wrong?

    Please help!

  • 378. Fjiorea  |  February 19th, 2009 at 12:53 am

    Dimi, try this code to output your image:

    <img src="{custom:thumbnail}"/>

    and if you want the image to be linked to your post search result as well, try:

    <a href="{url}"><img src="{custom:thumbnail}"></a>

    Hope that helps

  • 379. Fjiorea  |  February 20th, 2009 at 6:40 pm

    Now that I played around with the series of Plugins- Similar post, Popular post, Recent post and Random post. I noticed a problem with compatability.

    It seems whenever This(these) Plugin scans the posts, other plugin such as smartyoutube or viper’s video quicktags will be unable to properly scan for their tag code within the post content and embed videos.

    Is there a get around for this?

  • 380. haber  |  February 20th, 2009 at 11:30 pm

    thanks for plugin

  • 381. Widge  |  February 25th, 2009 at 6:47 am

    Quick addendum: removed the plugin using the plugin’s removal tool, deleted the plugin from the server, then reuploaded and reactivated it from scratch…and now every post is None Found. Well, at least there’s no line of demarcation any longer.

  • 382. Miguel  |  March 2nd, 2009 at 5:45 am

    hello, im using this plugin and i have a question.
    i want to use

    <?php $key = get_post_meta($post->ID,'key', true); ?>
    <?php echo($key); ?>

    in my similar posts but i didnt really understood your explanation for {php} (sorry, im not american)

    could you please help me?

  • 383. Adriana  |  March 3rd, 2009 at 7:28 pm

    I installed the plugin, and also library one that was mentioned to install. I placed the code: to the index, and I keep getting a fatal error:

    Fatal error: Call to undefined function: similar_posts() in /home/14822/domains/ on line 91

    My goal is to have a space with 6 recent posts of one category only, and this would include the actual images from the post too.

    What should I do to resolve the fatal error?

    Thank you for your time.

  • 384. Adriana  |  March 3rd, 2009 at 7:29 pm

    I’ve also deactivated and reactivated it again to see if that would help.

  • 385. Adriana  |  March 3rd, 2009 at 7:30 pm

    Oh, sorry, I’m on the latest WordPress version.

  • 386. Joni  |  March 4th, 2009 at 4:45 pm

    Hi, I have wordpress version 2.7.1 and was using your Similar Posts plugin. Similar Posts

    Well I keep getting messages from my host about high CPU usage so I deactivated most of my plugins and am slow adding them back to see which one or ones is causing the high CPU usage. Well it looks like Similar Posts causes my load usage to go up. Have you any problem like that? I have deactivated it again and will try to activate it in a couple of days and check once more on the CPU usage.

    You say that you have used 60 WordPress plugins together? No problems with high CPU usage? What host are you with?

  • 387. Joni  |  March 4th, 2009 at 5:12 pm

    When I deactivate this plugin my site is messed up (page doesn’t load all the way) and I still have the words, “Related Articles…” at the bottom of single posts. I tried looking in the theme files for, “recent_posts” (like you say to look for above, does that need updating?) but cannot find any assurance of it.

    I did look for and find the words, “Related Articles…” (which I guess I had added in) and I put in this code…

    if (function_exists('similar_posts')) { similar_posts(); }

    But all that did was put that code on my pages, but my pages did load OK this time. I also tried the code…

    <?php if (function_exists('similar_posts')) { similar_posts(); }

    But that make the page not able to load anything so I removed it.

    So when I try to reactive your plugin what code do I have to add to the single post file?

  • 388. shawn  |  March 7th, 2009 at 12:59 am

    i need to know how i would get a small line of text from that particular post under the link in the similar posts section to show up.

    like this:

    - the sky is falling and i can’t run away

    today the sky fell and i just can’t run away cause it…

  • 389. Widgett Walls  |  March 22nd, 2009 at 10:26 am

    Okay, I finally, after lots of tinkering, found a series of settings that would get me back working again. Not sure why my old settings suddenly quit working, but regardless, the link on my name should take you to the blog post where I provide screenshots of what wound up working for me. Hope that helps some people.

  • 390. Webmaster seo blog  |  March 24th, 2009 at 9:38 am

    Thanks for share….

    Its work for my blog

  • 391. Alan  |  March 25th, 2009 at 4:35 pm

    This plugin blows up when using FastCGI. I get an error:

    WordPress database error Incorrect string value: ‘/XE2 read…’ for column ‘content’ at row 1575 for query UPDATE wp_similar_posts SET content=”my stuff”…

    The post still goes through, but I get this annoying error message every time I post or update. Anyone have a clue?

  • 392. amaury  |  April 4th, 2009 at 9:45 pm

    Congratulations for these awesome plugin !
    I’m trying to display the similar post inline but I can’t make it :(
    I’ve tried the CSS styles
    .similar-post ul {display: inline}
    .similar-post ul li {display: inline}
    .similar-post li {display: inline}

    any of these properties works
    can you please help me ?
    thxs a lot

  • 393. Saki Sozleri  |  April 28th, 2009 at 2:21 pm

    I’ve also deactivated and reactivated it again to see if that would help.

  • 394. kate  |  April 29th, 2009 at 2:44 am

    Hi … loving this (and the other) plugins! I am using {image} and would like the related images to show up on the same line (horizontally) rather than vertically up and down. Is this possible?

    Thanks so much!

  • 395. Duncan | The Gastronomer's Bookshelf  |  April 30th, 2009 at 4:46 am

    I’ve loved this plugin for ages but have only just seen that it’s now possible to add images.

    Can anyone tell me how to display thumbnails which aren’t stored in a custom field? Just using {image} results in the full size image. Thanks in advance.

  • 396. kate  |  April 30th, 2009 at 2:09 pm

    Duncan — As long as you want to continue using the first image in the post, you can easily adjust the size. Try this:


    You can play around with the 100px to make the images larger or smaller depending on what you want. (You can remove the :link if you don’t want to image to be clickable.

    Hope that helps!

    Does anyone have any ideas about how to make the images display in a horizontal line rather than vertically? (See 2 comments up). THANKS!

  • 397. Duncan | The Gastronomer's Bookshelf  |  May 1st, 2009 at 1:20 am

    Kate — thanks so much for the comment. I appreciate the suggestion of that code and might use it… but my concern is the load time on resized full images, so accessing a thumbnail instead is the preferred solution if there is one out there!

    I was thinking about your horizontal line issue — at a guess, you could do an unordered list styled display:inline ? Something along those lines.

  • 398. Kheldon  |  May 5th, 2009 at 3:35 pm


    First off, great plugin.

    Second, I’m having a problem with the settings page. The settings do not load for me. I see the main settings page with the sub pages such as General, Output, Filter, etc. But None of them contain any options.

    If I click on one, I see the title of the subpage and the save button, but nothing in between.

    The only one that works is Managing the Index, which I don’t really want to mess with anyway.

    On Report a Bug and Remove this plugin, I don’t see the title or the save/submit button.

    Any ideas?


  • 399. José Luís  |  May 6th, 2009 at 5:50 am


    I had a compatibility problem with Similar Posts and WP-Email. After WP-Email successfully sends the e-mail, it shows the post again but without its content. Similar Posts then showed an SQL error because the post ID wasn’t set (“SELECT title, content, tags FROM wp_similar_posts WHERE pID= LIMIT 1″), like Rob in Denver (comment #66).

    I changed the function sp_terms_by_textrank() as you suggested to do with terms_to_match() and it now works fine.

    Can you verify if this workaround is correct and implement it on new versions?

  • 400. satranç  |  May 9th, 2009 at 8:47 pm

    thank you for you

  • 401. satranç  |  May 9th, 2009 at 8:48 pm

    thanks for the plugin!!!

  • 402. smellycat  |  May 21st, 2009 at 6:25 pm

    How can I chance the font’s size of the related posts?

  • 403. FreewareMatter  |  June 5th, 2009 at 7:16 pm

    How about the performance of this plugin? I mean, if it check the posts’ body to find related posts, it may cause the high load on server. I need a light related post plugin, can this plugin satisfy me?

  • 404. Marc (Webanhalter)  |  June 16th, 2009 at 7:22 pm

    Hi, do you still develop the plugins? Will it work under WordPress 2.8?

  • 405. craig  |  June 18th, 2009 at 12:10 pm


    when a new post is added the similar posts displays as none found, untill i click “Recreate Index” then the similar posts are displayed.

    How can i set the “Recreate Index” to auto run every time a new post is created, or if i set up a cron job what code would i execute?

  • 406. Joni  |  June 18th, 2009 at 3:23 pm

    >How about the performance of this plugin? I mean, if it check the posts’ body to find related posts, it may cause the high load on server. I need a light related post plugin, can this plugin satisfy me?

    I too would love to know if this wordpress plugin will cause high CPU usage.

    >Hi, do you still develop the plugins? Will it work under WordPress 2.8?

    This too — will it work right with WordPress 2.8 and are you still planning to keep it updated?

  • 407. Joni  |  June 18th, 2009 at 3:32 pm

    I too would love to know if this wordpress plugin will cause high CPU usage.

    This too — will it work right with WordPress 2.8 and are you still planning to keep it updated?

  • 408. Joni  |  June 26th, 2009 at 3:44 pm

    still would like to know if this works ok with 2.8 and how is the CPU usage?

  • 409. technochakra  |  July 2nd, 2009 at 9:02 am

    Just started using the plug-in. Very nice. Thanks for the effort you put into it.

  • 410. Angelo  |  August 3rd, 2009 at 6:19 am

    I upgraded wordpress, and now I see nothing coming up for related posts. Is anyone else having this problem, or did I do something wrong?

  • 411. Angelo  |  August 3rd, 2009 at 6:57 am

    Nevermind, it works fine… just a problem with my theme when updated.

  • 412. Helena  |  August 24th, 2009 at 8:43 pm

    Hello I love you plugins! all of them!

    Today i found this under Filter settings >> categories to exclude/include :
    Warning: str_repeat() [function.str-repeat]: Second argument has to be greater than or equal to 0 in /customers/ on line 593
    Is ‘t something to worry about?

    Thanks Helena

  • 413. çekmeköy kahvalti  |  August 15th, 2011 at 10:58 am

    Just started using the plug-in. Very nice. Thanks for the effort you put into it.

  • 414. Jeffrey Smith  |  August 24th, 2011 at 4:52 am

    Rob, I was having issues with this plugin, but found my answers here on your blog! Thank you for being so active in the success of your plugin and the success of others! Your plugin is really great for keeping people on my blog and delivering even more value! Really appreciate you!

  • 415. morrisjfwong  |  July 20th, 2013 at 3:12 pm

    Oh…try to use this plug in my blog, works well and reliable. Thank you for these sharing and openning. Great job!! Thanks you.

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