Swapping two variables without using a third variable

Swapping two variables without using a third variable is an interesting problem that can be solved using various techniques. Here are a few different methods to achieve variable swapping in PHP:

1. Using Arithmetic:

$a = 5;
$b = 10;

$a = $a + $b; // $a now holds the sum
$b = $a - $b; // $b now holds the original value of $a
$a = $a - $b; // $a now holds the original value of $b

2. Using Bitwise XOR:

$a = 5;
$b = 10;

$a = $a ^ $b;
$b = $a ^ $b;
$a = $a ^ $b;

3. Using Addition and Subtraction:

$a = 5;
$b = 10;

$a = $a + $b;
$b = $a - $b;
$a = $a - $b;

4. Using Multiplication and Division:

$a = 5;
$b = 10;

$a = $a * $b;
$b = $a / $b;
$a = $a / $b;

5. Using List and Explode:

$a = 5;
$b = 10;

list($b, $a) = explode(',', "$a,$b");

6. Using XOR and Addition:

$a = 5;
$b = 10;

$a = $a ^ $b;
$b = $a ^ $b;
$a = $a ^ $b;
$a = $a + $b;
$b = $a - $b;
$a = $a - $b;

7. Using List and Array:

$a = 5;
$b = 10;

list($a, $b) = [$b, $a];

8. Using Destructuring Assignment (PHP 7.1+):

$a = 5;
$b = 10;

[$a, $b] = [$b, $a];

9. Using XOR, Subtraction, and Negation:

$a = 5;
$b = 10;

$a = $a ^ $b;
$b = $a ^ $b;
$a = $a ^ $b;
$b = -$b;

Remember that while these techniques are interesting, in real-world scenarios, it’s often clearer and more maintainable to use a temporary variable for variable swapping.