3v4l.org

run code in 200+ php & hhvm versions
Bugs & Features
<?php $var = [ 'a' => 'a', 'b' => 'b', ]; array_walk($var, function ($value) { }); var_dump(key($var));
Output for 7.1.0 - 7.2.0
string(1) "a"
Output for 5.5.0 - 7.0.20
NULL