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Codex Resources

Function Reference/WP Cache

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.

Tip: Make sure define('WP_CACHE', true); is above this block:

 /* That's all, stop editing! Happy blogging. */
 if ( !defined('ABSPATH') )
       define('ABSPATH', dirname(__FILE__) . '/');
    require_once(ABSPATH . 'wp-settings.php');

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:

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