PHP foreach 循环中条件语句未多次执行的深层原因分析与解决方案

// 错误的订单数据结构构建方式示例
function readOrdersWrong($filename) {
    $orders = [];
    $lines = file($filename, FILE_IGNORE_NEW_LINES | FILE_SKIP_EMPTY_LINES);
    foreach ($lines as $line) {
        $data = explode(',', $line); // 假设订单数据是逗号分隔
        $orderId = $data[0];
        $customerId = $data[1];
        $amount = $data[2];
        // 错误：如果$customerId或$orderId不是全局唯一且被用作键，就会发生覆盖
        // 例如，如果$customerId被用作键，则一个客户的多个订单会互相覆盖
        $orders[$customerId] = [
            'order_id' => $orderId,
            'customer_id' => $customerId,
            'amount' => $amount
        ];
    }
    return $orders;
}

101,CUST001,50.00
102,CUST002,75.50
103,CUST001,120.00
104,CUST003,30.00
105,CUST001,80.00

<?php

// 模拟客户数据
$customers = [
    'CUST001' => ['id' => 'CUST001', 'name' => 'Alice'],
    'CUST002' => ['id' => 'CUST002', 'name' => 'Bob'],
    'CUST003' => ['id' => 'CUST003', 'name' => 'Charlie'],
];

/**
 * 正确读取订单文件并构建订单列表的函数
 * 返回一个包含所有订单的索引数组，每个订单都是一个关联数组。
 */
function readOrdersCorrect($filename) {
    $orders = [];
    if (!file_exists($filename)) {
        return $orders;
    }
    $lines = file($filename, FILE_IGNORE_NEW_LINES | FILE_SKIP_EMPTY_LINES);
    foreach ($lines as $line) {
        $data = explode(',', $line);
        if (count($data) >= 3) {
            $order = [
                'order_id' => trim($data[0]),
                'customer_id' => trim($data[1]),
                'amount' => (float)trim($data[2])
            ];
            // 将每个订单作为一个独立的元素添加到$orders数组中
            // 这样不会发生键值覆盖
            $orders[] = $order;
        }
    }
    return $orders;
}

// 主逻辑部分
if ($_SERVER['REQUEST_METHOD'] == 'GET') {
    if (isset($_GET['customer'])) {
        $requestedCustomerId = $_GET['customer'];

        // 检查请求的客户是否存在
        if (isset($customers[$requestedCustomerId])) {
            $requestedCustomer = $customers[$requestedCustomerId];

            // 使用正确的数据读取函数
            $allOrders = readOrdersCorrect('orders.txt');

            echo "<h2>客户订单详情：{$requestedCustomer['name']} (ID: {$requestedCustomer['id']})</h2>";
            echo "<table border='1'>";
            echo "<thead><tr><th>订单ID</th><th>金额</th></tr></thead>";
            echo "<tbody>";

            $hasOrders = false;
            // 遍历所有订单，筛选出当前客户的订单
            foreach ($allOrders as $order) {
                if ($order['customer_id'] == $requestedCustomer['id']) {
                    echo "<tr>";
                    echo "<td>{$order['order_id']}</td>";
                    echo "<td>{$order['amount']}</td>";
                    echo "</tr>";
                    $hasOrders = true;
                }
            }

            if (!$hasOrders) {
                echo "<tr><td colspan='2'>该客户没有订单。</td></tr>";
            }

            echo "</tbody>";
            echo "</table>";

        } else {
            echo "<p>未找到客户ID: {$requestedCustomerId}</p>";
        }
    } else {
        echo "<p>请在URL中提供客户ID，例如: ?customer=CUST001</p>";
    }
}
?>

array(5) {
  [0]=>
  array(3) {
    ["order_id"]=> string(3) "101"
    ["customer_id"]=> string(7) "CUST001"
    ["amount"]=> float(50)
  }
  [1]=>
  array(3) {
    ["order_id"]=> string(3) "102"
    ["customer_id"]=> string(7) "CUST002"
    ["amount"]=> float(75.5)
  }
  [2]=>
  array(3) {
    ["order_id"]=> string(3) "103"
    ["customer_id"]=> string(7) "CUST001"
    ["amount"]=> float(120)
  }
  [3]=>
  array(3) {
    ["order_id"]=> string(3) "104"
    ["customer_id"]=> string(7) "CUST003"
    ["amount"]=> float(30)
  }
  [4]=>
  array(3) {
    ["order_id"]=> string(3) "105"
    ["customer_id"]=> string(7) "CUST001"
    ["amount"]=> float(80)
  }
}