WP Super-Cache Not Deleting Expired Pages

WP Super Cache is a static caching plugin for WordPress. It generates html files that are served directly by Apache without processing comparatively heavy PHP scripts. By using this plugin you will speed up your WordPress blog significantly. ADVERTISEMENTS This plugin is a fork of the excellent WP-Cache 2 by Ricardo Galli Granada. WP-Cache 2 caches the pages of your WordPress blog and delivers them without accessing the database. Unfortunately it still means loading the PHP engine to serve the cached files. WP Super Cache gets around that. When it is installed, html files are generated and they are served without ever invoking a single line of PHP. How fast can your site serve graphic files? That? (almost) as fast it will be able to serve these cached files. If your site is struggling to cope with the daily number of visitors, or if your site appears on Digg.com, Slashdot or any other popular site then this plugin is for you.

How it works

A classic method of preparing an under powered site for a Digg front page appearance or a Slashdotting has been to manually save copies of dynamically generated pages, and place them in directories that match the permalinks structure. This method of performance enhancement does help servers handle a higher load without crashing, but is only effective when an oncoming rush of traffic can be anticipated. WP-Cache alone, while helpful, is not adequate in many cases, so WP Super Cache was created to effectively mimic the manual page caching method, but to handle it in an automated fashion. When a visitor who is not logged in, or who has not left a comment, visits they will be served a static HTML page out of the supercache subdirectory within the WordPress cache directory. If you navigate to that directory you can view an exact replica of your permalink structure as well as the HTML files within the directories. To determine if a page has been served out of the Super Cache, view the source and the last line on the page should read <!-- super cache --> or <!-- super cache gz -->. If a visitor who is logged in or who has left a comment views a cached page, it will be served from the standard WP Cache function and the last line in the source code will read <!-- Cached page served by WP-Cache -->

Features/Changes from WP-Cache

• A plugin and hooks system. A common complaint with WP Cache was that hacking was required to make it work nicely with other plugins. Now you can take advantage of the simple plugin system built in to change how or when pages are cached. Use do_cacheaction() and add_cacheaction() like you would with WordPress hooks. Plugins can add their own options to the admin page too.
• Works well with WordPress MU in VHOST or non-VHOST configuration. Each blog? cache files are identified to improve performance.
• Normal WP-Cache files are now split in two. Meta files go in their own directory making it much faster to scan and update the cache.
• Includes this WP-Cache and protected posts fix.
• Automatically disable gzip compression in WordPress instead of dying.
• As Akismet and other spam fighting tools have improved, the cache will only be invalidated if a comment is definitely not spam.
• A ?ock down?button. I like to think of this as my ?igg Proof?button. This basically prepares your site for a heavy digging or slashdotting. It locks down the static cache files and doesn? delete them when a new comment is made.
• Automatic updating of your .htaccess file. (Backup your .htaccess before installing the plugin!)
• Don? super cache any request with GET parameters.
• Better version checking of wp-cache-config.php and advanced-cache.php in case you?e using an old one.
• Better support for Microsoft Windows.
• Properly serve cached static files on Red Hat/Cent OS systems or others that have an entry for gzip in /etc/mime.types.
• The Reject URI function now uses regular expressions.

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