How to clone posts / populate form based on other posts

That wouldn't work for this case.

I have a code that's almost working. It's able to clone every field except for groups.

Here's how it's looking like so far:

// duplicate all post meta
$post_meta = get_post_meta( $post_id );
if( $post_meta ) {
	foreach ( $post_meta as $meta_key => $meta_values ) {
		foreach ( $meta_values as $meta_value ) {
			add_post_meta( $new_post_id, $meta_key, $meta_value );
		}
	}
}

How could I improve this so it'll also be able to go through the subfields?