list random friends

Hello, I have this code:

    $friends = $owner->listFriends('', $num, array(
        'size' => 'tiny',
        'pagination' => FALSE,
        'list_type' => 'gallery',
        'gallery_class' => 'elgg-gallery-users',
        'count' => TRUE
        ));

If I set $num to say 10, is it possible to return 10 random friends instead of the same 10 everytime? I know this is possible, just not sure how to do it. Thanks.