来请问一个有关问题

<br><?php <br />define('ACCESE',1);<br>require('../init.php');<br><br>$_GET['gid'] = (int)$_GET['gid'];<br>$_GET['num'] = (int)$_GET['num'];<br><br>$goods = new goodsModel();<br>$goods-&gt;db();<br>$cart = cart::getCart();<br><br>switch($_GET['act']) {<br>        //添加商品<br>        case 'buy':{<br>                $result = $goods-&gt;select_goods("g_id = $_GET[gid] and g_sale=1 and g_del=0");<br>                $g = $goods-&gt;db-&gt;fetch_array($result);<br>                //有此商品<br>                if(!empty($g)) { //判断商品是否存在<br>                        if($g['g_no']                                 $type = 'error';<br>                                $msg = '放到购物车添加失败（可能是库存不足或者管理员私吞了）';<br>                                include(ROOT.'view/home/tip.html');<br>                                exit;<br>                        }<br>                        //商品存在<br>                        $cart-&gt;addItem("$g[g_id]","$g[g_name]","$g[g_price]","$_GET[num]");   //----------------------此行报错<br>                } else {<br>                        $type = 'error';<br>                        $msg = '放到购物车添加失败（可能是下架、删除或者管理员私吞了）';<br>                        include(ROOT.'view/home/tip.html');<br>                        exit;<br>                }<br>                break;<br>        }<br><br>}<br><br>$title = '购物车 - 商城系统';<br>$path = '购物车';<br>include(ROOT.'view/home/cart.html');<div class="clear"></div>