3v4l.org

run code in 300+ PHP versions simultaneously
<?php function ack($m, $n) { if (!$m) return ++$n; elseif (!$n) return ack($m-1, 1); return ack($m-1, ack($m, $n-1)); } echo ack(4, 1);
Output for 5.3.7 - 5.3.29, 5.4.0 - 5.4.45, 5.5.24 - 5.5.35, 5.6.7 - 5.6.28, 7.0.0 - 7.0.20, 7.1.0 - 7.1.10, 7.2.0 - 7.2.33, 7.3.12 - 7.3.33, 7.4.0 - 7.4.33, 8.0.0 - 8.0.30, 8.1.0 - 8.1.28, 8.2.0 - 8.2.18, 8.3.0 - 8.3.6

Process exited with code 137.

preferences:
192.49 ms | 404 KiB | 252 Q