public static function confirmation()
 {
     if (empty($_SESSION['data'])) {
         header('Location: index.php');
     }
     if (isset($_POST['submit'])) {
         $ref = $_POST;
         $old = $_SESSION['data'];
         if ($ref['invoiceID'] === $old['invoiceID']) {
             Form::sendMail($old);
             Form::checkIn($old);
         } else {
             echo 'Invoice Didnt Matched!';
         }
         session_destroy();
     }
 }