Assigns a subscriber to a certain list if a certain link has been clicked

Add user to list after click on link

function my_add_user_to_list_after_click_on_link (  $subscriber_id, $campaign_id, $target, $index ){
    
    $link = 'http://example.com';
    $list_id = 123;
    $remove_from_old_lists = false;
    
    if( $link == $target ){
    
        mymail('subscribers')->assign_lists($subscriber_id, $list_id, $remove_from_old_lists);
    
    }
    
}

add_action( 'mymail_click', 'my_add_user_to_list_after_click_on_link', 10, 4);