public function clear($check)
    {
        if ($check) {
            return true;
        }
        if (class_exists('APCuIterator', false)) {
            $iterator = new APCuIterator(
                '/^' . preg_quote($this->_config['prefix'], '/') . '/',
                APC_ITER_NONE
            );
            apcu_delete($iterator);

            return true;
        }

        $cache = apcu_cache_info(); // Raises warning by itself already
        foreach ($cache['cache_list'] as $key) {
            if (strpos($key['info'], $this->_config['prefix']) === 0) {
                apcu_delete($key['info']);
            }
        }

        return true;
    }