- var_dump: documentation ( source)
- array_merge: documentation ( source)
<?php
$array1 = array(0 => 'zero_a', 2 => 'two_a', 3 => 'three_a');
$array2 = array(1 => 'one_b', 3 => 'three_b', 4 => 'four_b');
$result = array_merge($array1,$array2);
var_dump($result);