WordPress Development

Want to test super speed caching?

Yesterday morning was one of those mornings. I couldn’t sleep, but not for want of trying. Around 5am our 17 month old baby wasn’t too keen on the whole notion of shut-eye. Instead I took him downstairs to feed him, and do a little surfing and hacking to pass the time until the sun rose.

Lucky for you that I did.

I discovered that WP Super Cache was compressing the page output twice! That’s right, it’s my own fault, but for over a year that little bug has gone unnoticed. I won’t bore you with details, but it’s fixed now and if you compare wp-cache-phase2.php from the latest release with that in the development version you’ll spot the differences.

In testing, I noticed that pages were generated more quickly. Sometimes twice as fast as before if everything else had been cached by the object cache. I even posted a message to the support forum asking people to try it out but the silence is deafening which is why I’m turning to the power of the blog post.

If you’d like to give this bit of code a go, grab the development version of WP Super Cache, test it, and leave a comment here. Before you install it, grab a few pages while not logged in and record the page generation time, then after install, check out the same pages. I’d love to hear if it improves things.

You could also try setting “$cache_rebuild_files” to 1 in wp-cache-config.php. That will enable some experimental code that moves supercache files out of the way when the page becomes stale but then restores them while the page is being rebuilt. That should help significantly on busy sites where lots of comments are made. It’ll be switched off by default because I don’t think it will benefit most sites, and will only result in more I/O. Check out this forum thread for further info.

If you’re interested in testing the plugin in the future, you could subscribe to the wp-super-cache-dev tag, where I’ll post development updates on the plugin.


WP Super Cache 0.6.7

WP Super Cache is a plugin for WordPress that creates cached copies of your blog posts and pages, making your site much faster to serve. It’s also ideal for coping with sudden surges of traffic.

I released a new version of the plugin this morning. This is a bugfix release:

  • Mike Beggs contributed a number of changes:
    1. Better support for Win32 NTFS
    2. Better use of the “Vary” header so proxy servers won’t cache the wrong page. If you see leakage of comment details on posts this will fix that problem.
    3. WP-Cron handles cleanup of expired cache files in the background now.
    4. Disable mod_deflate if it’s running as it sometimes tries to compress gzipped files. Remove wp-content/cache/.htaccess for that file to be updated.
  • Lazy and Otto both recommended using get_comment() instead of the depreciated get_commentdata()
  • A basic “uninstall” function has been added to remove some of the files the plugin creates. It’s called when you deactivate the plugin.
  • PHP running as a CGI doesn’t support apache_request_headers() so that’s been added too.
  • And I almost forgot, the admin page received a slight makeover.

Get the plugin from the download page!


WP Super Cache 0.6.2

A few people stumbled across a strange bug in WP Super Cache. If your index.php was cached by the plugin then feeds or other pages that hadn’t been cached would show the front page!

A simple way to fix this is by adding “index.php” to the list of rejected URIs, but then it won’t be cached at all. This release fixes the problem but also allows index.php to be cached by the WP Cache engine, much better than excluding index.php completely.

Also included is a new feature that inserts your rewrite rules in a new .htaccess block. That will stop WordPress overwriting the rules after doing an upgrade, or after changing permalinks. The plugin won’t update your .htaccess if it finds the rules already in the “WordPress” section, but if you visit your permlinks options page and hit “Save Changes” the plugin rules will be deleted. Go to the WP Super Cache admin page where you can update the rules again. They’ll be inserted in a “WPSuperCache” block above the WordPress rule block.

If all that seems a bit technical, just go to your permalinks options page and hit “Save Changes” without changing anything, then update your rewrite rules on the Super Cache options page!

Go grab the plugin from the usual place.

I never saw this obscure problem because I redirect hits to /index.php to / using this mod_rewrite rule and php code. This used to help avoid duplicate content rules but I think Google is smarter now. It probably will help reduce pagerank dilution because all requests will go to one homepage url, rather than two.

RewriteRule ^index\.html / [R=301,L]

if( $_SERVER[ 'REQUEST_URI' ] == '/index.php' ) {
    header( "Location:", 301 );

Thanks to Dax (NSFW text) who figured out the problem with index.php caching.


Caching WordPress with WP-Cache in a spam filled world

WP-Cache and spam. Who’d have thought they were related? Unfortunately they are because when your blog is spammed WP-Cache doesn’t check if the comment is legitimate or not and deletes cached files related to the spammed post.

I noticed this happened a lot on In after I added thumbnails to the top of the page. The thumbnails change when the page is regenerated but I noticed that they would change much more frequently than expected. After some debugging I realised that comment spam was invalidating the WP-Cache cache.

How do you fix this? Here’s a small patch that can be applied to wp-cache-phase2.php, version 2.0.19 (and probably lower) that checks if the submitted comment was moderated or not. You’ll also find wp-cache-phase2.txt below. Just rename that to .php and copy it into your plugins/wp-cache/ folder for it to work.

Remember to update WP-Cache too. Despite last year’s date on the above post, it was updated as recently as last month!


  1. wp-cache-phase2.diff
  2. wp-cache-phase2.txt

Patch will be on it’s way to gallir in a few moments but if you’re using WP-Cache this could be a big help to your site. (and if you use Ultimate Tag Warrior I hope you’re using my patch?)


WPMU Update – Improved Caching

Hopefully you should see this site run a little faster, I’ve moved most database accesses to inside the cache loop.
For most users caching and processing of requests should be faster as the whole WordPress posts-loop is now cached, however there is a trade off. I can’t check if there are multiple or single posts on a page so every page, including the front page, is cached with your comment credentials and user login (if any). In other words, if I visit the front page and then you do, the front page won’t be cached for you, but if two anonymous users visit the second visitor will get a completely cached copy.
If you see any problems please leave a comment on this post, or email me at donncha @!

A bit later…I’m watching the logs and I’m glad I made that change. We’re being hit by 240 280 attempts at referer spamming from sex After the first hit, all they get served is static html! 🙂