Cache Class

ExpressionEngine’s Cache Class gives developers easy ways to cache data (strings, arrays, objects) in a key-value store. The storage driver can be either file-based or memory-based. More about supported drivers and configuration can be found under Data Caching and Performance.

Unlike the Session Cache, items stored using the Cache class can persist across multiple page loads because cache items are either stored on disk or in a memory-based cache store not dependent on ExpressionEngine.

It’s highly recommended you use the Cache Class when possible instead of manually writing to a cache directory so that cache items can be easily managed and seamlessly moved to a memory-based cache store so those with high traffic or network file systems can take advantage of the speed and versatility a memory-based cache offers and not be bogged down by file locks and I/O limitations on the disk.

This class is initialized by the system automatically so there is no need to do it manually.

Namespacing

You may want an extra layer of organization to your cache items, either for easy management or to prevent collisions with other keys in the system.

For example, let’s say we have an add-on called MyAddon and we want to make sure our cache keys don’t conflict with any others in ExpressionEngine, whether they be from other add-ons or native code. We’ll save and access our data like so:

ee()->cache->save('/myaddon/mykey', $data);
$data = ee()->cache->get('/myaddon/mykey');

We can go even further and nest our namespacing as deep as we want for further organization:

ee()->cache->save('/myaddon/entries/239', $data);

Where this comes in handy is clearing subsets of our own cache. If a condition arises in which we must flush all the items in our /entries/ namespace, we make this call to Cache::delete:

ee()->cache->delete('/myaddon/entries/');

With that, all the items we saved under /entries/ will be deleted while the rest of the items stored under our root namespace are kept. We can also clear the entire cache for our add-on without flushing out cache items for other add-ons or native components:

ee()->cache->delete('/myaddon/');

Namespacing gives you granular control over which items in your cache should be purged without affecting other parts of your add-on or ExpressionEngine.

Note: When flushing a namespace, the key must end with the namespace separator (/) so the Cache class knows to clear a namespace instead of trying to delete a key with the name of your namespace.

Scoping

Items stored in the cache by default are scoped to the site currently saving or retrieving from the cache. This prevents cache keys from colliding when the same keys are used in multiple sites in the same ExpressionEngine install.

But you may want the same cache item available across all sites in your ExpressionEngine install. In that case, you must specify a global scope by passing the Cache::GLOBAL_SCOPE constant when saving or retrieving from the cache:

ee()->cache->save('mykey', $data, 500, Cache::GLOBAL_SCOPE);
ee()->cache->get('mykey', Cache::GLOBAL_SCOPE);

By default, the scope parameter is Cache::LOCAL_SCOPE. Setting a global scope allows cache keys to be shared across the installation, while a local scope keeps keys specific to individual sites.

Class Methods

class Cache

save($key, $value[, $ttl = 60[, $scope = Cache::LOCAL_SCOPE]])

Given a key and a value to store, stores the item to the cache with the specified expiration time and namespace:

ee()->cache->save('/mymodule/mykey', $results, 3600);

get($key[, $scope = Cache::LOCAL_SCOPE])

Returns a previously saved item from the cache:

$data = ee()->cache->get('/mymodule/mykey');

delete($key[, $scope = Cache::LOCAL_SCOPE])

Deletes an item from the cache:

ee()->cache->delete('/myaddon/mykey');

Or deletes all items under a particular namespace:

ee()->cache->delete('/myaddon/');

clean([$scope = Cache::LOCAL_SCOPE])

Flushes the entire cache for the specified scope. Specifying a scope of Cache::GLOBAL_SCOPE clears the cache for the entire installation.

ee()->cache->clean();

cache_info()

Returns information about items stored in the cache under the current caching driver:

$info = ee()->cache->cache_info();

get_metadata($key[, $scope = Cache::LOCAL_SCOPE])

Returns metadata about a particular item in the cache:

$info = ee()->cache->get_metadata('/myaddon/mykey');

is_supported()

Checks to see if appropriate extensions and resources are available for a driver to determine if it is usable for caching:

ee()->cache->memcached->is_supported();

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