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How to Enable the Default WordPress Object Cache

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.

Enable 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..

Step 1: Enable the caching mechanism

Open wp-config.php and set the value of ENABLE_CACHE to “TRUE”:

define('ENABLE_CACHE', TRUE);

Step 2: Create the cache directory

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

/wp-content/cache/

Step 3: Make the cache folder writable

Ensure that the folder is writable by setting its permissions to 755 or 777.

Done!

Testing

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 server1
  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!

Winning

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.

Wrapping

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.

Footnotes

  • 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 ;)

Jeff Starr
About the Author Jeff Starr = Designer. Developer. Producer. Writer. Editor. Etc.
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32 responses
  1. Thank you for this post.

    But what about chmod 777 ?

    Is it safe ?

    Thanks

  2. The point that you mentioned, “saving you bandwidth”, I am quite sure that it might still be the same. But I am definitely sure that the Web Server CPU usage will drop down dramatically.

  3. Indeed, it won’t save any bandwidth.

    A noteworthy aspect of caching (be it WP-Cache, the built-in cache or whatever): whenever your blog takes ages to load and you have no clue where the problem comes from, just delete the /cache folder. More often than you’d think, it will fix everything.
    On Dreamhost, I simply deactivated the cache on all the blogs I run because it was locking too often (I think the efficiency of it depends on some NFS configuration)

  4. Jeff Starr

    @Rasheed: If you are able, you should definitely use 755 over 777. 755 grants fewer permissions and is thus the preferable choice, however, this setting does not always work under all circumstances and on all servers, whereas 777 — although not ideal — generally does the trick.

    @DeepFreeze: Yes, I see that now, I honestly don’t know what I was thinking (if anything) when I wrote that. I suppose it made sense at the time.. I guess that’s what I get for self-editing my content. I will definitely be fixing this — thanks for pointing it out ;)

    @Ozh: Ouch! It hurts now ;) Sorry for the misinformation! Also, thank you for mentioning the “cure-all” cache-deletion trick. I have experienced this myself on more than one occasion, including, oddly enough, setting up the WP cache itself. It is a strange, frequently useless beast, I concur, however, it may prove beneficial for certain individuals and/or specific situations. Hopefully, this post will help shed some light on the overall implementation process.

  5. ;-), Anytime Bro Anytime

  6. More Options for WP-Cache:

    define('ENABLE_CACHE', true); // Cache on
    define('CACHE_EXPIRATION_TIME', 604800); // Cachetime in seconds

    and a small Plugin for control the cache:
    http://bueltge.de/wordpress-cache-kontrollieren/479/

    You can clear the cache with one click.
    With best regards
    Frank

  7. Jeff Starr

    Frank,

    Thanks for reminding us about the CACHE_EXPIRATION_TIME option.. I was going to mention it in the article, but apparently failed to do so, for some reason or other..

    Also thanks for sharing the WordPress Cache Controller plugin with us — I am sure users will find it useful! Clearing the cache with a single click is definitely sweet ;)

    Cheers,
    Jeff

  8. Welcome!

    I have update this plugin with small addon. The plugin clear the cache, when you puplish, edit or delete comment and when you cjange private to puplish. You must not click, this functions is automaticly.
    With best regards and sorry for my bad english.
    Frank

  9. Jeff Starr

    Very good, Frank — thank you for sharing the update news with us!

    Cheers,
    Jeff

  10. Jeff Starr

    Hi Abhinav Singh, thanks for taking the time share your experience with us. Your frustration with the WordPress Object Cache is shared by many, including myself, hence the tutorial above. Hopefully you realize that the file-based object cache has been removed from all WordPress versions 2.5 or better. Looking at the site you linked to in your comment, it looks like you are running WordPress 2.5. Perhaps this is the issue?

    Regardless of any specific problems you might be having, I have to emphasize that the methods described in my tutorial are peer-reviewed and quite sound. They have worked for a number of people running various versions of WordPress in a variety of different environments.

    Btw, you shouldn’t fake your Feedburner subscriber count — it is dishonest, desperate, and makes you look like a real loser :(

  11. Abhinav Singh October 15, 2008 @ 12:37 pm

    For me this never worked.

    I tried deleting the cache folder, enable disable the things a few times but I could never see any files being generated in the cache folder.

    Sorry, but your post sucked for me :(

  12. Abhinav Singh October 15, 2008 @ 1:32 pm

    Man it worked when I followed the steps and installed WP-Cache-2. So I am not sure where the problem was. Now I can see the cache files in the cache folder

    And kuddos to you man. You are the first one who has found that out from over a thousand visitors to my site.

    So now probably its time to release this hack where people can put the same on their sites :) Nothing that I am a looser, I created this as a hack. Though to release this for everyone, but then help myself back till someone picks me up on this ;)

    Kuddos dude ;)

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