public static function int2bytes($len, $int = 0, $l = false)
    {
        $hexstr = dechex($int);

        if ($len === null) {
            if (strlen($hexstr) % 2) {
                $hexstr = "0" . $hexstr;
            }
        } else {
            $hexstr = str_repeat('0', $len * 2 - strlen($hexstr)) . $hexstr;
        }

        $bytes = strlen($hexstr) / 2;
        $bin   = '';

        for ($i = 0; $i < $bytes; ++$i)
        {
            $bin .= chr(hexdec(substr($hexstr, $i * 2, 2)));
        }

        return $l ? strrev($bin) : $bin;
    }