php code question

Question

<?php
$x = "a";
$y = "b";
$x ^= $y;
$y ^= $x;
$x ^= $y;
echo $x; //Got b
echo $y; //Got a
?>

why it gives that results ; does "a" and "b" have an particular value???

Answer 1

"a" and "b" have a numeric value associated with their character position in the ASCII table: actually 97 and 98.
you can verify with: echo ord($x);
The ^= operator assigns the Binary XOR (exclusive or) result of the two values.

This is a well known "hack" to swap two numbers, you can read more about how it works:
https://en.wikipedia.org/wiki/XOR_swap_algorithm