// check if the value are not empty
 if (!empty($_POST["username"]) && !empty($_POST["password"]) && !empty($_POST["repeat_password"]) && !empty($_POST["email"]) && !empty($_POST["role"])) {
     // take out the value from the $_POST array
     $username = $_POST["username"];
     $password = $_POST["password"];
     $repeat_password = $_POST["repeat_password"];
     $role = $_POST["role"];
     $email = $_POST["email"];
     // check if the two password match
     if ($password === $repeat_password) {
         // include a global file with all the classes
         require_once 'Matchup.inc.php';
         // create an object of MUUsers
         $user = new MUUsers();
         // check if the username is already in use
         if (!$user->isUserAlreadyRegistered($username)) {
             // check if the registration was successful
             if ($user->registerUser($username, $password, $email, $role)) {
                 // user is correctly registered
                 $register_response_success = "1";
                 $register_response_message = "Utente%20registrato%20con%20successo";
             } else {
                 // something wrong happen
                 $register_response_success = "0";
                 $register_response_message = "Qualcosa%20di%20inaspettato%20e'%20accaduto";
             }
         } else {
             // user already register
             $register_response_success = "0";
             $register_response_message = "Utente%20gia'%20registrato";
         }