3v4l.org

run code in 300+ PHP versions simultaneously
<?php $check = ['a', 'b', 'c']; $actual = ['a' => 'one', 'b' => 'two', 'c' => 'three']; $result=array_diff_key(array_flip($check), array_keys($actual)); echo '<pre>'; print_r($result);

preferences:
44.88 ms | 2110 KiB | 5 Q