Cache invalidation

FileCache provides explicit methods to invalidate cached entries when they are no longer valid.

Remove a specific cache entry by calling the invalidate method:

$cache->invalidate("user-profile");

Check whether a cache's key is valid with the checkValidity method:

if($cache->checkValidity("user-profile")) {
	// do something ...
}

Automatic invalidation

When constructing the Cache class, the $secondsValid parameter is used to indicate how long a cache is valid for. The default value is 1 hour. After the time expires, the cache will become invalid, so the next time the cache is read, the callback function will be executed to refresh the cache.