private static function getInc($s_bits, $x)
    {
        $lsb = self::getLSB($s_bits, $x);
        $X = self::toUInt32Bits($lsb) + 1;
        $res = self::getMSB(self::getLength($x) - $s_bits, $x).pack('N', $X);

        return $res;
    }
private static function getInc($s_bits, $x)
    {
        $lsb = self::getLSB($s_bits, $x);
        $X = self::toUInt32Bits($lsb) + 1;
        $res = self::getMSB(self::getLength($x) - $s_bits, $x).pack('N', $X);

        return $res;
    }
@param int $s_bits
@param int $x

@return string