The PHP array_udiff_uassoc() function compares the keys/values of two or more arrays, and returns the entries from array1 not in the other array(s).

This function uses two user-defined functions for comparison. The key is used in the first function and the value is used in the second.

Both the keys and values are compared. Both must be a match.

<?php
function my_function_key($a, $b) {
    if ($a===$b) {
        return 0;
    }
    return ($a>$b)?1:-1;
}

function my_function_value($a, $b) {
    if ($a===$b) {
        return 0;
    }
    return ($a>$b)?1:-1;
}

$a1 = array('Car 1' => 'Lamborghini', 'Car 2' => 'Alfa Romeo', 'Car 5' => 'Maserati');
$a2 = array('Car 1' => 'Lamborghini', 'Car 2' => 'Ferrari', 'Car 3' => 'Maserati');

$result = array_udiff_uassoc($a1, $a2, 'my_function_value', 'my_function_key');
print_r($result);
?>

Array ( [Car 2] => Alfa Romeo [Car 5] => Maserati )

array_udiff_uassoc(array1, array2, array3, ..., myfunc_key, myfunc_value)