PHP array in if else

I'm still in my PHP basic training, but I want to show multiple meta_boxes when a post is 'specialisaties'. I'm loading 1 meta box, but I need to add another one called 'url, $meta_boxes = url_post_meta_boxes();

} else if ($post->post_type == 'specialisaties') {
    $meta_boxes = specialisaties_post_meta_boxes();
}

How do I change the else if to load multiple $meta_boxes?