php 会话数组如果 ID 相同则添加一个元素

Question

我得到以下会话数组来存储购物车项目：

print_r($_SESSION['items']):

Array
(
    [0] => Array
        (
            [p_name] => Product A
            [p_price] => 13.90
            [p_seller] => 2001
        )

    [1] => Array
        (
            [p_name] => Product B
            [p_price] =>  2.00
            [p_seller] => 2002
        )

    [2] => Array
        (
            [p_name] => Product C
            [p_price] => 1.20
            [p_seller] => 2002
        )

    [3] => Array
        (
            [p_name] => Product D
            [p_price] => 50.00
            [p_seller] => 2001
        )

)

我有一个从数据库调用额外数据的循环：

while($res = $shipment->fetch_object()){
    $seller_id = $res->seller;
    $shipment_cost = $res->shipment_fee;
    
    //array_push($_SESSION['items']['p_fee'], $shipment_cost);
}

让我们说，在循环中我得到以下数据：

$seller_id = 2001; $shipment_cost = 5.00

$seller_id = 2002; $shipment_cost = 3.00

我想将名称为 ['p_fee'] 的额外元素分配并添加到其各自的组 ['p_seller']

if $seller_id(2001) == ['p_seller'] ---> array_push($_SESSION['items']['p_fee'], '5.00') }

if $seller_id(2002) == ['p_seller'] ---> array_push($_SESSION['items']['p_fee'], '3.00') }

可以吗？

$_SESSION['items'] 最终可能包含如下元素：

Array
(
    [0] => Array
        (
            [p_name] => Product A
            [p_price] => 13.90
            [p_seller] => 2001
            [p_fee] => 5.00
        )

    [1] => Array
        (
            [p_name] => Product B
            [p_price] =>  2.00
            [p_seller] => 2002
            [p_fee] => 3.00
        )

    [2] => Array
        (
            [p_name] => Product C
            [p_price] => 1.20
            [p_seller] => 2002
            [p_fee] => 3.00
        )

    [3] => Array
        (
            [p_name] => Product D
            [p_price] => 50.00
            [p_seller] => 2001
            [p_fee] => 5.00
        )

)

Answer 1

是的，你可以。

您可以通过添加值，同时从数据库中检索它来完成此操作。例如：

while($res = $shipment->fetch_object()){
    $seller_id = $res->seller;
    $shipment_cost = $res->shipment_fee;

    foreach ($_SESSION['items'] as $key => $item) {
        if ($item['p_seller'] === $seller_id) {
            $_SESSION['items'][$key]['p_fee'] = $shipment_cost;
        }
    }
}

更好（更快）的方法是在 sellerId 和 costs 之间创建一个映射，然后将其放入会话中：

$costMapping = array();
while($res = $shipment->fetch_object()){
    $seller_id = $res->seller;
    $shipment_cost = $res->shipment_fee;

    $costMapping[$seller_id] = $shipment_cost;
}

foreach ($_SESSION['items'] as $key => $item) {
    if (isset($costMapping[$item['p_seller']])) {
        $_SESSION['items'][$key]['p_fee'] = $costMapping[$item['p_seller']];
    }
}

这样你只有2个循环，不管你有多少卖家。

Answer 2

是可以的，你应该做两个循环，首先是收取费用，其次是将它们与项目相关联。

// Fill the fees first
$fees = [];
while($res = $shipment->fetch_object()){
    $seller_id = $res->seller;
    $shipment_cost = $res->shipment_fee;
    $fees[$seller_id] = $shipment_fee;
}

// Assign fees
foreach ($_SESSION['items'] as &$item) {
    $fee = $fees[$item['p_seller']] ?: 0; // <- fee will be 0 if not found !
    $item['p_fee'] = $fee;
}

希望这对您有所帮助:)

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