How to Enable the Default WordPress Object Cache

By Jeff Starr on Wednesday, December 26, 2007 — 29 Responses metadata

Post #464 categorized as WordPress, last updated on Feb 15, 2009
Tagged with cache, optimize, tutorials, WordPress

Recently, while attempting to optimize site performance, I found myself experimenting with various caching mechanisms currently available for WordPress. Specifically, I explored each of the following caching options:

• WP-Cache 2 [WordPress plugin]
• WP Super Cache [WordPress plugin]
• WordPress Object Cache [built-in caching mechanism]

While working with the two plugins, WP Cache 2 and Super Cache, I was pleased to discover crystal-clear instructions on each their respective sites. Having access to installation and usage information greatly facilitated the implementation of each of these caching techniques.

On the other hand, finding information about the default WordPress object cache proved virtually impossible. Finally, after locating some decent information, I was able to confirm my initial suspicions and subsequently decided to post a quick article outlining and describing this very straightforward caching method. Although enabling the WordPress cache turns out to be drop-dead easy, it is always good to be sure that you aren’t forgetting a step or otherwise overlooking some important aspect of the process.

How to enable the default WordPress cache in 3 easy steps

Note: This information applies to WordPress versions less than 2.5 only.

Ready? Implementing the default WordPress object cache is remarkably simple:

1) Enable the caching mechanism — open your wp-config.php file and set the value of ENABLE_CACHE to “TRUE”:

define('ENABLE_CACHE', TRUE);

2) Create the cache directory — create a folder called “cache” and place it within the wp-content directory:

/wp-content/cache/

3) Make the cache folder writable — ensure that the folder is writable by setting its permissions to 755 or 777.

Once you have everything setup, surf around your site and check things out by reloading a few different pages. If the WordPress default object cache is working correctly, you will see a newly added slew of temporary cache files along with a newly created index.php file and wp_object_cache.lock file within the cache directory. Thus, if you don’t see any such files in the cache directory after surfing around your site, go back and recheck that you have correctly executed the proper steps. Note: if nothing seems to be happening with your cache — i.e., no cache files are being generated — you may want to try “rebooting the cache” via the following procedure:

1. Disable the cache in wp-config.php
2. Delete the cache directory completely from your server ¹
3. Create a new cache directory, set the permissions, and re-enable caching in wp-config.php

I have also had luck simply deleting the cache directory and letting WordPress recreate it automatically. Remember, if it doesn’t work the first few times, try a few more times before giving up — it does work!

After you have confirmed that the object cache is working, you’re done. From that point on, or until you disable it, the cache should work as intended, saving you bandwidth resources and saving your visitors time. To verify this, navigate to a long-lost post that is buried way back in your archives somewhere — something that is completely off the radar. As you visit, note the page loading time. Now, visit the page again and compare the results. On average, while the native object cache is nowhere near as effective as either plugin method, it does manage to shave off a noticeable amount of loading time for your visitors. Although the WordPress object cache may not work as well as either of the cache plugins currently available, it is an effective caching method that is a breeze to setup and run. And, best of all, the default caching mechanism works perfectly with virtually all WordPress plugins.

¹ Note: One final note concerning the WordPress object cache: all of the files may be safely deleted at your discretion — everything is regenerated automagically ;)

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