The simplest syntax to do swaping in PHP

swap.php

<?php

/**
 * This works.
 */
$a = 1; $b = 2;
echo "Before swap: {$a}, {$b}\n";
list($a, $b) = [$b, $a];
echo "After swap: {$a}, {$b}\n";

// result:
// Before swap: 1, 2
// After swap: 2, 1