3v4l.org

run code in 300+ PHP versions simultaneously
<?php $foo = function () use (&$ref) { return $ref = ["foo" => &$foo]; }; $a = $foo(); $ref["foo"] = 2; var_dump($a);
Output for 7.0.0 - 7.0.20, 7.1.0 - 7.1.33, 7.2.0 - 7.2.33, 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
array(1) { ["foo"]=> NULL }
Output for 5.5.0 - 5.5.36, 5.6.0 - 5.6.28
array(1) { ["foo"]=> &int(2) }
preferences:
91.58 ms | 1806 KiB | 4 Q