3v4l.org

run code in 200+ php & hhvm versions
Bugs & Features
<?php $a = array(); $a['key'][][] = 1; var_dump($a);
Output for 4.3.0 - 7.1.7
array(1) { ["key"]=> array(1) { [0]=> array(1) { [0]=> int(1) } } }