3v4l.org

run code in 300+ PHP versions simultaneously
<?php $a = array('a'=>1,'b'=>2,'c'=>3); $b = array('a'=>'aa','b'=>'bb'); var_dump(array_combine( array_map( function($key) use ($b) { return isset($b[$key]) ? $b[$key] : $key; }, array_keys($a) ), array_values($a) ));

preferences:
26.75 ms | 402 KiB | 5 Q