- print_r: documentation ( source)
- array_merge: documentation ( source)
<?php
// Init Arrays
$arrayOne = ['one' => 1, 'two' => 2, 'three' => 3];
$arrayTwo = ['one' => 9, 'two' => 9, 'four' => 4];
print_r($arrayOne + $arrayTwo);
print_r(array_merge($arrayOne, $arrayTwo));