- array_diff_assoc: documentation ( source)
- var_dump: documentation ( source)
- array_merge: documentation ( source)
<?php
$base = ['one' => 10];
$arr1 = ['one' => 1, 'two' => 2];
$arr2 = ['three' => 3];
var_dump(array_merge($arr1, $arr2, $base));
var_dump(array_diff_assoc(array_merge($arr1, $arr2)), $base);