php - PHP/MySQL 无法获取购物车总计

Question

我试图获取我的购物车的总数，但我似乎无法让它工作，我想知道这是否是我处理代码的方式，我使用了 foreach 循环从 session 中获取 id数组，然后循环遍历结果，但是当我尝试进行 SUM 查询时，答案只是将各个价格输出为数组，而不是将它们加在一起。将价格存储在二维数组中会更好吗？

if(!isset($_SESSION['cart'])){//
$_SESSION['cart']=array();//creating session array to store items id
}
    <?php
                        echo'<table class="table">';
                            echo'<tr>';
                            echo'<th>Item</th>';
                            echo'<th>Code</th>';
                            echo'<th>Description</th>';
                            echo'<th>Cost(GBP)</th>';
                            echo'<th>Remove</th>';
                            echo'</tr>';

                            foreach ($_SESSION['cart'] as $value){
                                $z = mysql_query('SELECT * FROM product_item where id="'.$value.'"');
                                while($row = mysql_fetch_array($z)){
                                    echo'<tr>';
                                    echo'<td><img src="images/'.$row['path'].'.jpg" alt="'.$row['alt'].'" width="65" height="65"/></td>';
                                    echo'<td>'.$row['code'].'</td>';
                                    echo'<td>'.$row['description'].'</td>';
                                    echo'<td><p>&pound;'.$row['price'].'</p></td>';
                                    echo'<td><p><a title="remove from shopping cart" href="cart.php?remove='.$value.'">X</a></p></td>';
                                    echo'</tr>';                                
                                }


                                // this is where i want to get total cost
                                $y = mysql_query('SELECT SUM(price) as total_cost FROM product_item where id="'.$value.'"');
                                while($row = mysql_fetch_array($y)){
                                    echo $row['total_cost'];
                                }

                            }

                            echo'<tr>';
                            echo'<td></td>';
                            echo'<td></td>';
                            echo'<td></td>';
                            echo'<td><p>Total</p></td>';
                            echo'<td></td>';
                            echo'</tr>';
                            echo'</table>';
                        }
                    ?>
                    ?>

Answer 1

为什么不是外部变量？

if(!isset($_SESSION['cart'])){//
$_SESSION['cart']=array();//creating session array to store items id

$cartTotal = 0; //This is where you store the total
}
    <?php
                        echo'<table class="table">';
                            echo'<tr>';
                            echo'<th>Item</th>';
                            echo'<th>Code</th>';
                            echo'<th>Description</th>';
                            echo'<th>Cost(GBP)</th>';
                            echo'<th>Remove</th>';
                            echo'</tr>';

                            foreach ($_SESSION['cart'] as $value){
                                $z = mysql_query('SELECT * FROM product_item where id="'.$value.'"');
                                while($row = mysql_fetch_array($z)){
                                    $cartTotal += $row['price'];
                                    echo'<tr>';
                                    echo'<td><img src="images/'.$row['path'].'.jpg" alt="'.$row['alt'].'" width="65" height="65"/></td>';
                                    echo'<td>'.$row['code'].'</td>';
                                    echo'<td>'.$row['description'].'</td>';
                                    echo'<td><p>&pound;'.$row['price'].'</p></td>';
                                    echo'<td><p><a title="remove from shopping cart" href="cart.php?remove='.$value.'">X</a></p></td>';
                                    echo'</tr>';                                
                                }
                            }
                            echo $cartTotal; //after running through all the items, you can show the total

                            echo'<tr>';
                            echo'<td></td>';
                            echo'<td></td>';
                            echo'<td></td>';
                            echo'<td><p>Total</p></td>';
                            echo'<td></td>';
                            echo'</tr>';
                            echo'</table>';
                        }
                    ?>
                    ?>