public static function addTime($key, $time)
    {
        static::$with_meta = true;

        $cache = static::get($key);

        static::$with_meta = false;

        if ($cache == null) {
            return false;
        }

        if ($cache['__bow_meta']['expire_at'] == '+') {
            $cache['__bow_meta']['expire_at'] = time();
        }

        $cache['__bow_meta']['expire_at'] += $time;

        return (bool) file_put_contents(
            static::makeHashFilename($key),
            serialize($cache)
        );
    }