3v4l.org

run code in 300+ PHP versions simultaneously
<?php $arr = ['one' => 1, 'two' => 2, 'three' => 3]; $keys =['one', 'two', 'three']; $merged = array_diff(array_count_values(array_merge($keys, array_keys($arr))), [2]); var_dump($merged);

preferences:
26.06 ms | 408 KiB | 5 Q