PHPを使用して簡単な電子商取引機能を開発する方法

<?php
if ($_SERVER['REQUEST_METHOD'] === 'POST') {
   // 获取用户提交的表单数据
   $username = $_POST['username'];
   $password = $_POST['password'];

   // 将数据插入到用户表中
   $sql = "INSERT INTO users (username, password) VALUES ('$username', '$password')";
   
   // 执行SQL语句
   // ...
}
?>
<form method="POST" action="register.php">
   <input type="text" name="username" placeholder="用户名">
   <input type="password" name="password" placeholder="密码">
   <button type="submit">注册</button>
</form>

<?php
if ($_SERVER['REQUEST_METHOD'] === 'POST') {
   // 获取用户提交的表单数据
   $username = $_POST['username'];
   $password = $_POST['password'];

   // 查询用户表中是否有匹配的用户名和密码
   $sql = "SELECT * FROM users WHERE username='$username' AND password='$password'";
   
   // 执行SQL查询
   // ...
}
?>
<form method="POST" action="login.php">
   <input type="text" name="username" placeholder="用户名">
   <input type="password" name="password" placeholder="密码">
   <button type="submit">登录</button>
</form>

<?php
// 查询商品表中的所有商品
$sql = "SELECT * FROM products";

// 执行SQL查询
// ...

// 遍历查询结果，展示商品信息
while ($row = mysqli_fetch_assoc($result)) {
   echo "<h3>{$row['name']}</h3>";
   echo "<p>{$row['description']}</p>";
   echo "<p>价格：{$row['price']}元</p>";
   echo "<a href='buy.php?id={$row['id']}'>购买</a>";
}
?>

<?php
if ($_SERVER['REQUEST_METHOD'] === 'POST') {
   // 获取用户提交的表单数据
   $productId = $_POST['productId'];
   $quantity = $_POST['quantity'];

   // 将订单数据插入到订单表中
   $sql = "INSERT INTO orders (user_id, product_id, quantity) VALUES ('$userId', '$productId', '$quantity')";
   
   // 执行SQL语句
   // ...
}
?>
<form method="POST" action="buy.php">
   <input type="hidden" name="productId" value="<?php echo $_GET['id']; ?>">
   <input type="number" name="quantity" placeholder="购买数量">
   <button type="submit">购买</button>
</form>