/**
  * Returns an instance of the form with a particular ID
  *
  * @access public
  * @static
  * @since 3.8.10
  *
  * @param int $id Optional. Defaults to 0. The ID of the form
  * @return WPSC_Checkout_Form
  */
 public static function &get($id = 0)
 {
     if (!self::$instances) {
         self::$instances[$id] = new WPSC_Checkout_Form($id);
     }
     self::$form_titles = get_option('wpsc_checkout_form_sets');
     return self::$instances[$id];
 }