You had a second set of form elements for mobile on the page that had the same form element names. When you do that you need each to have its own form tag so that a single form submit doesn't send two copies of each field. In this case it was picking up the mobile version which had no selection. I've corrected that problem and the redirect issue. Please download the Prod_detail.php page and Prod_results.php page that I've updated from your live server.