private function getFileKey(\SplFileInfo $file)
    {
        $key = null;

        if ($h = @fopen($file, 'r')) {
            rawurldecode(rtrim(fgets($h)));
            $value = stream_get_contents($h);
            fclose($h);
            $key = substr($value, 0, strpos($value, "\n"));
        }

        return $key;
    }