3v4l.org

run code in 300+ PHP versions simultaneously
<?php $a = [10, 2, 5, 10, 0]; $b = [1, 20, 11, 8, 3]; var_export( array_reduce( array_keys($b), fn ($result, $k) => array_replace($result, [$k => ($result[$k] ?? 0) + $b[$k]]), $a ) );
Output for 8.1.0 - 8.1.33, 8.2.0 - 8.2.29, 8.3.0 - 8.3.27, 8.4.1 - 8.4.14
array ( 0 => 11, 1 => 22, 2 => 16, 3 => 18, 4 => 3, )

preferences:
93.87 ms | 406 KiB | 5 Q