PHP array add and merge behave

Purpose

Compare between array add array()+array() and array_merge() in PHP.

Code:

<?php
$arr = array(
	'a' => 1,
	'b' => 1,
	0 => 1,
) + array(
	'a' => 2,
	'c' => 2,
	0 => 2,
);
var_export($arr);
$arr = array_merge( array(
	'a' => 1,
	'b' => 1,
	0 => 1,
) , array(
	'a' => 2,
	'c' => 2,
	0 => 2,
));
var_export($arr);

Result:

array (
  'a' => 1,
  'b' => 1,
  0 => 1,
  'c' => 2,
)
array (
  'a' => 2,
  'b' => 1,
  0 => 1,
  'c' => 2,
  1 => 2,
)