- var_dump: documentation ( source)
- array_merge: documentation ( source)
<?php
$first = ['a' => 1, 'b' => 2];
$second = ['a' => 3, 'd' => 4];
var_dump($first + $second);
var_dump(array_merge($second, $first));
var_dump(array_merge($second, $first) === $first + $second);