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