PHP - Bitwise XOR and assignment operator

The Bitwise XOR and assignment operator (^=) assigns the first operand a value equal to the result of Bitwise XOR operation of two operands.

(x ^= y) is equivalent to (x = x ^ y)

The Bitwise XOR operator (^) is a binary operator which takes two bit patterns of equal length and performs the logical exclusive OR operation on each pair of corresponding bits. It returns 1 if only one of the bits is 1, else returns 0.

The example below describes how bitwise XOR operator works:

50 ^ 25 returns 43

     50    ->    110010  (In Binary)
   ^ 25    ->  ^ 011001  (In Binary)
    ----        --------
     43    <-    101011  (In Binary)  

The code of using Bitwise XOR and assignment operator (^=) is given below:

<?php
$x = 50;
$y = 25;

//Bitwise XOR and assignment operation
$x ^= $y;

//Displaying the result
echo "x = $x";
?>

The output of the above code will be:

x = 43

Example: Swap two numbers without using temporary variable

The bitwise XOR and assignment operator can be used to swap the value of two variables. Consider the example below.

<?php
function swap($x, $y) {
  echo "Before Swap.\n";
  echo "x = $x \n";
  echo "y = $y \n";

  //Swap technique
  $x ^= $y;
  $y ^= $x;
  $x ^= $y;

  echo "After Swap.\n";
  echo "x = $x \n";
  echo "y = $y \n";
}

swap(10, 25);
?>

The above code will give the following output:

Before Swap.
x = 10
y = 25
After Swap.
x = 25
y = 10