Swap variables in PHP

varSwap.php

<?php
// Way 1
$a = $b + $a - ($b = $a);

// Way 2
list($b, $a) = array($a, $b);

// Way 3
function swap(&$a, &$b) {
    $tmp = $a;
    $a = $b;
    $b = $tmp;
}

// Way 4
$a ^= $b ^= $a ^= $b;