如何使用PHP开发微信小程序的购物清单功能？

<?php
// 连接数据库
$servername = "localhost";
$username = "username";
$passWord = "password";
$dbname = "dbname";
$conn = new mysqli($servername, $username, $password, $dbname);
if ($conn->connect_error) {
    die("连接失败: " . $conn->connect_error);
}

// 查询商品列表
$sql = "SELECT * FROM products";
$result = $conn->query($sql);
$products = array();
if ($result->num_rows > 0) {
    while($row = $result->fetch_assoc()) {
        $products[] = $row;
    }
}

// 返回结果
echo json_encode($products);
$conn->close();
?>

<?php
// 连接数据库
$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "dbname";
$conn = new mysqli($servername, $username, $password, $dbname);
if ($conn->connect_error) {
    die("连接失败: " . $conn->connect_error);
}

// 获取参数
$user_id = $_POST['user_id'];
$product_id = $_POST['product_id'];
$quantity = $_POST['quantity'];

// 添加商品到购物车
$sql = "INSERT INTO shopping_cart (user_id, product_id, quantity) VALUES ('$user_id', '$product_id', '$quantity')";
if ($conn->query($sql) === TRUE) {
    echo "添加成功";
} else {
    echo "添加失败";
}

$conn->close();
?>

wx.request({
  url: 'Http://localhost/products.php',
  success: function(res) {
    let productList = res.data;
    // 展示商品列表...
  }
})

wx.request({
  url: 'http://localhost/addToCart.php',
  method: 'POST',
  data: {
    user_id: '123',
    product_id: '456',
    quantity: '1'
  },
  success: function(res) {
    let result = res.data;
    // 处理添加结果...
  }
})