Item::model PHP Method

    public static function model($className = __CLASS__)
    {
        return parent::model($className);
    }

 /**
  * Displays a particular model.
  * @param integer $id the ID of the model to be displayed
  */
 public function actionAdditem($item_id)
 {
     $user_id = Yii::app()->user->id;
     // find the users cart
     $user = User::model()->find(array('condition' => 'id=:user_id', 'params' => array(':user_id' => $user_id)));
     // find the users cart
     $cart = Cart::model()->find(array('condition' => 'cart_owner=:cart_owner', 'params' => array(':cart_owner' => $user_id)));
     // find the item being reffered to by item_id
     $item = Item::model()->find(array('condition' => 'id=:item_id', 'params' => array(':item_id' => $item_id)));
     if (is_null($cart)) {
         // if the cart is not found. create a cart for the user.
         $cart = new Cart();
         $cart->cart_owner = $user->id;
         $cart->save();
     }
     // check if the same order was already made & increment else, create new
     $order = Order::model()->find(array('condition' => 'item_id=:item_id AND cart_id=:cart_id AND order_by=:order_by', 'params' => array(':item_id' => $item_id, ':cart_id' => $cart->id, ':order_by' => $user->id)));
     if (is_null($order)) {
         $order = new Order();
         $order->create_time = time();
         $order->quantity = 1;
         $order->item_id = $item->id;
         $order->cart_id = $cart->id;
         $order->order_by = $user->id;
     } else {
         $order->quantity = 1 + $order->quantity;
         $order->update_time = time();
     }
     $order->save();
     // find all orders by this user.
     $orders = Order::model()->findAll('cart_id=:cart_id AND order_by=:order_by', array(':cart_id' => $cart->id, ':order_by' => $user->id));
     $return = array('success' => true, 'data' => $orders);
     echo CJavaScript::jsonEncode($return);
     Yii::app()->end();
 }