hits * Number of keys that have been requested and found present. * * - misses * Number of items that have been requested and not found. * * - uptime * Time that the server is running. * * - memory_usage * Memory used by this server to store items. * * - memory_available * Memory allowed to use for storage. * * @return mixed[]|null An associative array with server's statistics if available, NULL otherwise. */ public function getStats(); }