3v4l.org

run code in 300+ PHP versions simultaneously
<?php $ids=array("a","b","c","d","e"); $groups=array(array("a","c"),array("c","e")); array_walk($groups,function($v,$i)use(&$ids){ $ids=array_diff($ids,$v); }); print_r($ids);

preferences:
43.68 ms | 402 KiB | 5 Q