ParagonIE\Halite\Util::xorStrings PHP Method

    public static function xorStrings(string $left, string $right) : string
    {
        $length = self::safeStrlen($left);
        if ($length !== self::safeStrlen($right)) {
            throw new InvalidType('Both strings must be the same length');
        }
        if ($length < 1) {
            return '';
        }
        /**
         * @var int[]
         */
        $leftInt = \unpack('C*', $left);
        /**
         * @var int[]
         */
        $rightInt = \unpack('C*', $right);
        $output = '';
        for ($i = 0; $i < $length; ++$i) {
            $output .= \pack('C', ($leftInt[$i + 1] ^ $rightInt[$i + 1]) & 0xff);
        }
        return $output;
    }