PHP Foreach循环中条件语句无法多次执行的深层原因与解决方案

<?php
if ($_SERVER['REQUEST_METHOD'] == 'GET') {
    if (isset($_GET['customer'])) {
        $requestedCustomer = $customers[$_GET['customer']];
        $orders = readOrders('orders.txt');
        // ... 之后可能有一个 foreach 循环来遍历 $orders
    }
}
?>

101,CUST001,Laptop,1
102,CUST002,Mouse,2
103,CUST001,Keyboard,1

<?php
function readOrders($filename) {
    $orders = [];
    $lines = file($filename, FILE_IGNORE_NEW_LINES | FILE_SKIP_EMPTY_LINES);
    foreach ($lines as $line) {
        list($orderId, $customerId, $item, $quantity) = explode(',', $line);
        // 错误：使用 customerId 作为 $orders 数组的主键
        $orders[$customerId] = [
            'order_id' => $orderId,
            'customer_id' => $customerId,
            'item' => $item,
            'quantity' => $quantity
        ];
    }
    return $orders;
}
?>

[
    'CUST001' => [
        'order_id' => '103', // 订单101被订单103覆盖
        'customer_id' => 'CUST001',
        'item' => 'Keyboard',
        'quantity' => '1'
    ],
    'CUST002' => [
        'order_id' => '102',
        'customer_id' => 'CUST002',
        'item' => 'Mouse',
        'quantity' => '2'
    ]
]

<?php
function readOrders($filename) {
    $orders = [];
    $lines = file($filename, FILE_IGNORE_NEW_LINES | FILE_SKIP_EMPTY_LINES);
    foreach ($lines as $line) {
        list($orderId, $customerId, $item, $quantity) = explode(',', $line);
        // 正确：使用 orderId 作为 $orders 数组的主键，确保每个订单都是唯一的条目
        // 或者，如果不需要通过 orderId 直接访问，也可以简单地 $orders[] = [...]
        $orders[$orderId] = [
            'order_id' => $orderId,
            'customer_id' => $customerId,
            'item' => $item,
            'quantity' => $quantity
        ];
    }
    return $orders;
}
?>

[
    '101' => [
        'order_id' => '101',
        'customer_id' => 'CUST001',
        'item' => 'Laptop',
        'quantity' => '1'
    ],
    '102' => [
        'order_id' => '102',
        'customer_id' => 'CUST002',
        'item' => 'Mouse',
        'quantity' => '2'
    ],
    '103' => [
        'order_id' => '103',
        'customer_id' => 'CUST001',
        'item' => 'Keyboard',
        'quantity' => '1'
    ]
]

<?php
// 假设 $customers 数组和 $requestedCustomer 已经从查询字符串获取
// 并且 $orders 数组已通过上述正确方式构建

if ($_SERVER['REQUEST_METHOD'] == 'GET' && isset($_GET['customer'])) {
    $customerId = $_GET['customer']; // 获取请求的客户ID

    // 假设 $customers 数组存储了客户信息，且键为客户ID
    $requestedCustomer = $customers[$customerId] ?? null; 

    if ($requestedCustomer) {
        $orders = readOrders('orders.txt'); // 调用上面修正后的函数

        echo "<h2>客户 " . htmlspecialchars($requestedCustomer['name'] ?? $customerId) . " 的订单列表</h2>";
        echo "<table border='1'>";
        echo "<tr><th>订单ID</th><th>商品</th><th>数量</th></tr>";

        $foundOrders = false;
        foreach ($orders as $orderId => $order) { // 遍历所有订单
            if ($order['customer_id'] == $customerId) { // 检查订单的 customer_id 是否匹配请求的客户ID
                echo "<tr>";
                echo "<td>" . htmlspecialchars($order['order_id']) . "</td>";
                echo "<td>" . htmlspecialchars($order['item']) . "</td>";
                echo "<td>" . htmlspecialchars($order['quantity']) . "</td>";
                echo "</tr>";
                $foundOrders = true;
            }
        }

        if (!$foundOrders) {
            echo "<tr><td colspan='3'>没有找到该客户的订单。</td></tr>";
        }
        echo "</table>";
    } else {
        echo "<p>未找到指定客户。</p>";
    }
} else {
    echo "<p>请通过 URL 参数指定客户ID，例如: ?customer=CUST001</p>";
}

// 示例 $customers 数组 (实际应从文件或数据库加载)
$customers = [
    'CUST001' => ['name' => '张三'],
    'CUST002' => ['name' => '李四'],
];

// 假设 readOrders 函数已定义如上
?>