- print_r: documentation ( source)
- array_diff: documentation ( source)
<?php
$array1 = array("a" => "green", "red", "blue", "red");
$array2 = array("b" => "green", "yellow", "red");
$result = array_diff($array1, $array2);
print_r($result);print_r($array1);print_r($array2);