PHPモール関数チュートリアル：ショッピングカートと注文同期機能の実装

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

<?php
// 获取用户ID和商品ID
$user_id = $_SESSION['user_id'];
$product_id = $_POST['product_id'];

// 检查购物车中是否已存在该商品记录
$query = "SELECT * FROM cart WHERE user_id = $user_id AND product_id = $product_id";
$result = mysqli_query($connection, $query);

if(mysqli_num_rows($result) == 0) {
    // 若购物车中不存在该商品记录，则添加一条新记录
    $query = "INSERT INTO cart (user_id, product_id, quantity, created_at, updated_at) VALUES ($user_id, $product_id, 1, NOW(), NOW())";
} else {
    // 若购物车中已存在该商品记录，则更新数量
    $query = "UPDATE cart SET quantity = quantity + 1, updated_at = NOW() WHERE user_id = $user_id AND product_id = $product_id";
}

mysqli_query($connection, $query);
?>

<?php
// 获取用户ID
$user_id = $_SESSION['user_id'];

// 获取购物车中的商品信息
$query = "SELECT * FROM cart WHERE user_id = $user_id";
$result = mysqli_query($connection, $query);

while($row = mysqli_fetch_array($result)) {
    $product_id = $row['product_id'];
    $quantity = $row['quantity'];
    
    // 将购物车中的商品信息添加至订单表中
    $query = "INSERT INTO orders (user_id, product_id, quantity, created_at) VALUES ($user_id, $product_id, $quantity, NOW())";
    
    mysqli_query($connection, $query);
}

// 清空购物车
$query = "DELETE FROM cart WHERE user_id = $user_id";
mysqli_query($connection, $query);
?>