I have an array with default settings, and one array with user-specified settings. I want to merge these two arrays so that the default settings gets overwritten with the user-specified ones.

I have tried to use array_merge, which does the overwriting like I want, but it also adds new settings if the user has specified settings that doesn't exist in the default ones. Is there a better function I can use for this than array_merge? Or is there a function I can use to filter the user-specified array so that it only contains keys that also exist in the default settings array?

(PHP version 5.3.0)

Example of what I want

$default = array('a' => 1, 'b' => 2);
$user = array('b' => 3, 'c' => 4);

// Somehow merge $user into $default so we end up with this:
Array
(
    [a] => 1
    [b] => 3
)