Codex

Codex Resources

Function Reference/WP Cache

Contents

Role of WP_Cache

WP_Object_Cache is WordPress' class for caching data which may be computationally intensive to regenerate dynamically on every page load. It's defined in wp-includes/cache.php.

Do not use the class directly in your code when writing plugins, but use the wp_cache functions listed here.

Caching to file to store the information across page loads is not enabled by default - this can be enabled by adding define('ENABLE_CACHE', true); to your wp-config.php file.

Within a single page loading caching does still occur so as to reduce the number of database queries as much as possible

wp_cache functions

Almost all of these functions take a:

  • key: the key to indicate the value
  • $data: the value you want to store
  • flag: optional: this is a way of grouping your cache data. If you use a flag, your data will be stored in a subdirectory of your cache directory
  • expire: number of seconds (by default 900) 
wp_cache_add($key, $data, $flag = '', $expire = 0)

This function first checks if there is a cached object on the given $key. If not, then it is saved, otherwise returns false. 

wp_cache_delete($id, $flag = '')

Clears a given file. 

wp_cache_get($id, $flag = '')

Gives back the value of the cached object if it did not expired. Otherwise gives back false. 

wp_cache_replace($key, $data, $flag = '', $expire = 0)

Replaces the given cache if it exists, returns false otherwise. 

wp_cache_set($key, $data, $flag = '', $expire = 0)

Sets the value of the cache object. If the object already exists, then it will be overwritten, if the object does not exists it will be created. 

wp_cache_init()

Initializes a new cache object. This function is called by Wordpress at initialization if cacheing is enabled. 

wp_cache_flush()

Clears all the cache files. 

wp_cache_close()

Saves the cached object. This function is called by Wordpress at the shutdown action hook.

Examples

You can use WP_Object_Cache and Snoopy to cache offsite includes: 

$news = wp_cache_get('news');
if($news == false) {
	$snoopy = new Snoopy;
	$snoopy->fetch('http://example.com/news/'); 
	$news = $snoopy->results;
	wp_cache_set('news', $news);
} 
echo $news;


Additional Resources

  • Dougal Campbell wrote a short guide on how to use the Wordpress Cache object from within your own plugins : Using the Wordpress Object Cache
  • Peter Westwood has a plugin to help people analyse the behaviour of the cache, provides the administrator with a quick overview of how the cache is performming and what queries are cached : WP Cache Inspect

This page is marked as incomplete. You can help Codex by expanding it.

Retrieved from "http://codex.wordpress.org/Function_Reference/WP_Cache"