<form method="post" action="add_to_cart.php">
<input type="hidden" name="product_id" value="123">
<input type="submit" value="添加到購物車">
</form>

<?php
//啟用會話
session_start();
//檢查是否存在購物車數組
if(!isset($_SESSION['cart_items'])){
$_SESSION['cart_items'] = array();
}
//獲取產品ID
$product_id = $_POST['product_id'];
//添加產品到購物車數組
array_push($_SESSION['cart_items'], $product_id);
//重定向到購物車頁面
header('Location: cart.php');
?>

<?php
//連接數據庫
$db = new mysqli('localhost', 'username', 'password', 'database_name');
//獲取購物車中的產品ID數組
$product_ids = $_SESSION['cart_items'];
//用IN運算符查詢所有產品
$query = "SELECT * FROM products WHERE id IN (" . implode(',', $product_ids) . ")";
$result = $db->query($query);
//循環遍歷結果集
while($row = $result->fetch_assoc()){
echo "<p>" . $row['name'] . "（價格：" . $row['price'] . "）</p>";
}
//關閉數據庫連接
$db->close();
?>