public static function forget($key)
    {
        $filename = static::makeHashFilename($key);

        if (!file_exists($filename)) {
            return false;
        }

        $r = (bool) @unlink($filename);

        $parts = explode('/', $filename);

        array_pop($parts);

        $dirname = implode('/', $parts);

        if (is_dir($dirname)) {
            @rmdir($dirname);
        }

        return $r;
    }