3v4l.org

run code in 300+ PHP versions simultaneously
<?php $hex = "abba test baab"; $hex = array_map(function ($x) { return ($x === 'a') ? 'b' : (($x === 'b') ? 'a' : $x); }, str_split($hex)); echo implode('', $hex);
Output for 7.0.0 - 7.0.33, 7.1.0 - 7.1.33, 7.2.0 - 7.2.34, 7.3.0 - 7.3.33, 7.4.0 - 7.4.33, 8.0.0 - 8.0.30, 8.1.0 - 8.1.34, 8.2.0 - 8.2.30, 8.3.0 - 8.3.30, 8.4.1 - 8.4.18, 8.5.0 - 8.5.3
baab test abba

preferences:
116.08 ms | 1804 KiB | 4 Q