public function __construct($elem, $params = array())
 {
     parent::__construct($elem, $params);
     //on s'assure d'avoir un nombre !
     if ($this->value !== "") {
         $this->value += 0;
     }
 }
 public function __construct($elem, $params = array())
 {
     parent::__construct($elem, $params);
 }