private function defaultCache()
    {
        if (extension_loaded('apcu') && class_exists('\\Cache\\Adapter\\Apcu\\ApcuCachePool')) {
            return new \Cache\Adapter\Apcu\ApcuCachePool();
        } elseif (extension_loaded('apc') && class_exists('\\Cache\\Adapter\\Apc\\ApcCachePool')) {
            return new \Cache\Adapter\Apc\ApcCachePool();
        }
        return null;
    }