3v4l.org

run code in 300+ PHP versions simultaneously
<?php $calc = function ($arg = null, $acc = '') use (&$calc) { return $arg === null ? $acc : function ($arg = null, $saved = '') use (&$calc, $acc) { var_dump($arg); return $calc($arg, $arg . $acc . $saved); }; }; $result = $calc(1)(3)(3)(8)(); var_dump($result);
Output for 7.0.0 - 7.0.20, 7.1.0 - 7.1.20, 7.2.6 - 7.2.33, 7.3.16 - 7.3.33, 7.4.0 - 7.4.33, 8.0.0 - 8.0.30, 8.1.0 - 8.1.27, 8.2.0 - 8.2.17, 8.3.0 - 8.3.4
int(3) int(3) int(8) NULL string(3) "833"

preferences:
135.24 ms | 403 KiB | 168 Q