private function _checkTtl($pFile, $pKey)
    {
        $ttl = $this->_files[$pFile][$pKey][static::AGL_CACHE_EXPIRE];
        if ($ttl > 0 and $ttl < $this->_time) {
            unset($this->_files[$pFile][$pKey]);
            $this->_save($pFile);

            return false;
        }

        return true;
    }