PHP开发的二手回收网站实现用户购物车功能

CREATE TABLE `cart_items` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `user_id` int(11) NOT NULL,
  `product_id` int(11) NOT NULL,
  `quantity` int(11) NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

<table>
  <tr>
    <th>商品</th>
    <th>单价</th>
    <th>数量</th>
    <th>小计</th>
    <th>操作</th>
  </tr>
  <?php
  // 查询购物车中的商品
  $user_id = $_SESSION['user_id'];
  $sql = "SELECT * FROM cart_items WHERE user_id = $user_id";
  $result = mysqli_query($conn, $sql);

  while ($row = mysqli_fetch_assoc($result)) {
    $product_id = $row['product_id'];

    // 查询商品信息
    $product_sql = "SELECT * FROM products WHERE id = $product_id";
    $product_result = mysqli_query($conn, $product_sql);
    $product_row = mysqli_fetch_assoc($product_result);
    ?>
    <tr>
      <td><?php echo $product_row['name']; ?></td>
      <td><?php echo $product_row['price']; ?></td>
      <td><?php echo $row['quantity']; ?></td>
      <td><?php echo $product_row['price'] * $row['quantity']; ?></td>
      <td>
        <a href="edit_quantity.php?id=<?php echo $row['id']; ?>">修改数量</a>
        <a href="delete_item.php?id=<?php echo $row['id']; ?>">删除</a>
      </td>
    </tr>
    <?php
  }
  ?>
</table>