/**
  * Display field
  * 
  * This method overwrites parent display method to include some hidden values
  */
 public function display()
 {
     parent::display();
     if (isset($_POST['s']) && isset($_POST['distance'])) {
         echo HTML::hiddenInput('s_old', $_POST['s']);
         echo HTML::hiddenInput('dist_old', $_POST['distance']);
         if ($this->value > 0) {
             echo HTML::hiddenInput('shoeid_old', $this->value);
         }
     }
 }