- var_dump: documentation ( source)
- array_replace_recursive: documentation ( source)
<?php
$parent = array(
'one' => 'ONE',
'three' => 'THREE',
);
$extended = array(
'two' => 'TWO',
'three' => '3',
'four' => 'FOUR',
);
var_dump($parent, $extended, array_replace_recursive($parent, $extended));