WordPress Object Cache Wrapper Class

A simple MU plugin for WordPress that acts as a wrapper for WP Object Cache functions, with support for flushing cache by group.

It was created as an MU plugin so that it is loaded and available for use in the theme as well as standard custom plugins, useful to cache heavy operations that fall outside of WordPress's built-in caching (such as direct database queries, file and remote operations, etc).

Installation

Simply copy the object-cache-helper.php file to your wp-content/mu-plugins directory (create one if it does not exist).

Usage

Class Instantiation

Without arguments:

$cache = new \MU_Plugins\WP_Cache_Object();

With arguments:

$cache = new \MU_Plugins\WP_Cache_Object([
   'expire' => HOUR_IN_SECONDS * 8,
   'group' => 'my_cache_group'
]);

Getting/Setting Cache Value

In this example, we will retrieve the public IP address of the server from SeeIP using an anonymous function as the callback and cache it for one day:

function get_public_ip_address() {
  $result = wp_remote_get( 'https://ip4.seeip.org' );
  return isset( $result['body'] ) ? $result['body'] : null;
}

$cache = new \MU_Plugins\WP_Cache_Object( [ 'expire' => DAY_IN_SECONDS ] );
$ip_address = $cache->get_object( 'my_server_public_ip_address', 'get_public_ip_address' );

echo 'Public IP Address: ' . $ip_address;

Note that in this example, we have one line of code in the callback function, but you can add as much logic as you like.

Anonymous Function as Callback

In this example, we will do the same as above with an anonymous function as the callback:

$cache = new \MU_Plugins\WP_Cache_Object( [ 'expire' => DAY_IN_SECONDS ] );

$ip_address = $cache->get_object( 'my_server_public_ip_address', function() {
  $result = wp_remote_get( 'https://ip4.seeip.org' );
  return isset( $result['body'] ) ? $result['body'] : null;
});

echo 'Public IP Address: ' . $ip_address;

Passing Variables to Callback Function

This example shows how to pass variables to an anonymous callback. You would not cache this in practice and purely serves as an example for passing variables. In this example, we pass $name and $age to the callback.

$cache = new \MU_Plugins\WP_Cache_Object( [ 'expire' => HOUR_IN_SECONDS * 12 ] );

$name = 'Daniel';
$age = 29;

$greeting = $cache->get_object( 'about_me_string', function() use ( &$name, &$age ) {
  return sprintf( 'Hello %s. You are %d years old.', $name, $age );
});

echo $greeting; // Hello Daniel. You are 29 years old.

Flushing the Cache

You can flush the entire cache using wp_cache_flush(), or you can flush a group that was created using this class with the following:

$cache->flush_group( 'my_cache_group' );

Deleting a Specific Key From a Cache Group

$cache->delete_group_key( 'my_cache_key_name' ); // Removes key from default group

$cache->delete_group_key( 'my_cache_key_name', 'custom_cache_group' ); // Removes key from specific group

Arguments

The following arguments are supported when instantiating the class:

Option	Description	Type	Default
group	The group to store the cache key in	string	{theme_dir}_cache_group
expire	Number of seconds to cache the value	int	3600 (1 hour)
single	Store as single key rather than group array	bool	false
network_global	Set to true to store cache value for entire network, rather than per sub-site	bool	false
force	Always return uncached value, useful for debugging	bool	false