php - 无法获取我的购物车中商品的总金额

Question

if (isset($_SESSION['cart'])) {
    foreach($_SESSION['cart'] as $key => $value) {
        $sql = "SELECT product_name, image, price, sum(price) AS subtotal  FROM 
        items WHERE id = '$key'
        ";
        $result = mysqli_query($conn, $sql);

        if (mysqli_num_rows($result) > 0) {
            $item = mysqli_fetch_assoc($result);
            extract($item);

        }
    }
}

我试图获取我的购物车的总金额，但是当我回显 $subtotal 时，我得到的不是总金额，而是仅一件商品的价格

Answer 1

您可以通过不同的方式获得总金额。

一种方法可以像这样更改查询

$ids = array();

if (isset($_SESSION['cart'])) {
    foreach($_SESSION['cart'] as $key => $value) {
        $ids[] = $key; //get all the ids
    }

    $ids = implode(',', $ids); //make the ids array a string like this 1,2,3...

    $sql = "SELECT product_name, image, price, sum(price) AS subtotal  FROM 
    items WHERE id IN ($ids)";
    $result = mysqli_query($conn, $sql);

    if (mysqli_num_rows($result) > 0) {
        $item = mysqli_fetch_assoc($result);
        extract($item);

    }
}