来请问一个有关问题

define('ACCESE',1);

require('../init.php');



$_GET['gid'] = (int)$_GET['gid'];

$_GET['num'] = (int)$_GET['num'];



$goods = new goodsModel();

$goods->db();

$cart = cart::getCart();



switch($_GET['act']) {

        //添加商品

        case 'buy':{

                $result = $goods->select_goods("g_id = $_GET[gid] and g_sale=1 and g_del=0");

                $g = $goods->db->fetch_array($result);

                //有此商品

                if(!empty($g)) { //判断商品是否存在

                        if($g['g_no'] < $_GET['num']) { //判断库存

                                $type = 'error';

                                $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）';

                                include(ROOT.'view/home/tip.html');

                                exit;

                        }

                        //商品存在

                        $cart->addItem("$g[g_id]","$g[g_name]","$g[g_price]","$_GET[num]");   //----------------------此行报错

                } else {

                        $type = 'error';

                        $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）';

                        include(ROOT.'view/home/tip.html');

                        exit;

                }

                break;

        }



}



$title = '购物车 - 商城系统';

$path = '购物车';

include(ROOT.'view/home/cart.html');