PHP Foreach 循环中条件语句未多次执行：数据结构与多对一关系处理

<?php
// 模拟从文件读取并错误地构建订单数组
// 假设 readOrders() 函数在处理时使用了 customer_id 作为键
function readOrdersProblematic($filePath) {
    $data = file($filePath, FILE_IGNORE_NEW_LINES | FILE_SKIP_EMPTY_LINES);
    $orders = [];
    foreach ($data as $line) {
        $parts = explode(',', $line);
        if (count($parts) >= 3) {
            $orderId = trim($parts[0]);
            $customerId = trim($parts[1]);
            $amount = floatval(trim($parts[2]));
            // 错误：使用 customerId 作为主键，会导致同客户订单覆盖
            $orders[$customerId] = ['order_id' => $orderId, 'customer_id' => $customerId, 'amount' => $amount];
        }
    }
    return $orders;
}

// 模拟 orders.txt 内容:
// ord_101,cust_001,100.00
// ord_102,cust_002,150.00
// ord_103,cust_001,200.00  // 这一行会覆盖 cust_001 的 ord_101
// ord_104,cust_001,50.00   // 这一行会覆盖 cust_001 的 ord_103

file_put_contents('orders.txt', "ord_101,cust_001,100.00\nord_102,cust_002,150.00\nord_103,cust_001,200.00\nord_104,cust_001,50.00");

$problematicOrders = readOrdersProblematic('orders.txt');

echo "<h3>错误的数据结构示例 (仅保留最后一条订单):</h3>";
echo "<pre>";
print_r($problematicOrders);
echo "</pre>";
// 预期输出：cust_001 只有 ord_104，ord_101 和 ord_103 被覆盖
// Array
// (
//     [cust_001] => Array
//         (
//             [order_id] => ord_104
//             [customer_id] => cust_001
//             [amount] => 50
//         )
//     [cust_002] => Array
//         (
//             [order_id] => ord_102
//             [customer_id] => cust_002
//             [amount] => 150
//         )
// )
?>

<?php
// 模拟从文件读取并正确构建订单数组
function readOrdersCorrect($filePath) {
    $data = file($filePath, FILE_IGNORE_NEW_LINES | FILE_SKIP_EMPTY_LINES);
    $orders = [];
    foreach ($data as $line) {
        $parts = explode(',', $line);
        if (count($parts) >= 3) {
            $orderId = trim($parts[0]);
            $customerId = trim($parts[1]);
            $amount = floatval(trim($parts[2]));
            // 正确：将每个订单作为一个独立的元素添加到数组末尾
            $orders[] = ['order_id' => $orderId, 'customer_id' => $customerId, 'amount' => $amount];
        }
    }
    return $orders;
}

file_put_contents('orders.txt', "ord_101,cust_001,100.00\nord_102,cust_002,150.00\nord_103,cust_001,200.00\nord_104,cust_001,50.00");

$correctOrders = readOrdersCorrect('orders.txt');

echo "<h3>正确的数据结构示例 (保留所有订单):</h3>";
echo "<pre>";
print_r($correctOrders);
echo "</pre>";
// 预期输出：所有订单都存在
// Array
// (
//     [0] => Array
//         (
//             [order_id] => ord_101
//             [customer_id] => cust_001
//             [amount] => 100
//         )
//     [1] => Array
//         (
//             [order_id] => ord_102
//             [customer_id] => cust_002
//             [amount] => 150
//         )
//     [2] => Array
//         (
//             [order_id] => ord_103
//             [customer_id] => cust_001
//             [amount] => 200
//         )
//     [3] => Array
//         (
//             [order_id] => ord_104
//             [customer_id] => cust_001
//             [amount] => 50
//         )
// )
?>

<?php
// 假设这是您的入口点，例如 index.php?customer=cust_001
if ($_SERVER['REQUEST_METHOD'] == 'GET' && isset($_GET['customer'])) {
    $requestedCustomerId = $_GET['customer'];

    // 假设 $customers 数组已加载，并包含客户信息
    // $customers = ['cust_001' => ['name' => 'Alice'], 'cust_002' => ['name' => 'Bob']];
    // $requestedCustomer = $customers[$requestedCustomerId];

    // 使用上面定义的正确读取函数
    $orders = readOrdersCorrect('orders.txt'); // 加载所有订单，每个订单都是一个独立元素

    echo "<h3>客户 {$requestedCustomerId} 的订单列表:</h3>";
    $foundOrders = false;
    foreach ($orders as $order) {
        // 检查订单的 customer_id 是否与请求的客户ID匹配
        if (isset($order['customer_id']) && $order['customer_id'] === $requestedCustomerId) {
            echo "订单ID: " . htmlspecialchars($order['order_id']) . ", 金额: " . htmlspecialchars($order['amount']) . "<br>";
            $foundOrders = true;
        }
    }

    if (!$foundOrders) {
        echo "未找到客户 {$requestedCustomerId} 的订单。";
    }
} else {
    echo "请通过 URL 参数提供客户ID，例如: ?customer=cust_001";
}
?>