Plugins can use a cache backend to improve performance. This can be done by specifying a cache backend with the setCacheBackend method in the manager's constructor. The following line of code will allow the Unit plugins to be cached and only discovered on a cache rebuild.

The $cache_backend variable is passed to the constructor. The second parameter provides the cache key. The cache key will have the current language code added as a suffix.

There is an optional third parameter that takes an array of strings to represent cache tags that will cause the plugin definitions to be cleared. This is an advanced feature, and plugin definitions should normally be cleared through the manager's clearCachedDefinitions method. The cache tags allow the plugin definitions to be cleared when a relevant cache is cleared as well.