array_diff_recursive

<?php

$arr1 = array(
        'key1' => 2,
        'key2' => 4,
        'key3' => array(1, 2,
                        array(1,4,3,5,
                              array(10, 13, 20)),
                        7),
        'key4' => 1,
);

$arr2 = array(
        'key1' => 2,
        'key2' => 5,
        'key3' => array(1, 2,
                        array(1,34,3,5,
                              array(10, 15, 20)),
                        7),

);

function array_diff_recursive($a1, $a2) {
    $result = array();

    foreach( $a1 as $k=>$v ) {
        if (array_key_exists($k, $a2)) {
            if ( is_array($v) && is_array($a2[$k]) ) {
                $result[$k] = array_diff_recursive($v, $a2[$k]);
            } else {
                if ( $v !== $a2[$k] ) {
                    $result[$k] = $v;
                }
            }
        } else {
             $result[$k] = $v;
        }
    }

    return $result;
}

$multi_diff = array_diff_recursive($arr1, $arr2);

// Tests
echo "<pre>";
echo "Array 1:\n";
print_r($arr1);
echo "\n\nArray 2:\n";
print_r($arr2);
echo "\n\nMulti diff:\n";
print_r($multi_diff);
echo "</pre>";
?>