class DataProcessor {
    private $internalConfig = ['mode' => 'secure'];

    public function processData($input) {
        // 这是一个公开的接口
        if ($this->validateInput($input)) { // 内部调用私有方法
            $processed = $this->applyBusinessLogic($input); // 内部调用保护方法
            return $processed;
        }
        return null;
    }

    protected function applyBusinessLogic($data) {
        // 这是一个受保护的方法，供子类或本类内部使用
        // 比如，具体的业务逻辑实现，可能需要被继承或重写
        echo "Applying business logic with mode: " . $this->internalConfig['mode'] . "/n";
        return strtoupper($data);
    }

    private function validateInput($input) {
        // 这是一个私有方法，仅供本类内部使用，不希望外部或子类直接调用
        echo "Validating input.../n";
        return !empty($input);
    }
}

class AdvancedDataProcessor extends DataProcessor {
    public function extendedProcess($input) {
        // 子类可以访问protected方法
        $result = $this->applyBusinessLogic($input);
        echo "Extended processing done./n";
        return $result;
    }
}

$processor = new DataProcessor();
echo $processor->processData("hello world") . "/n"; // OK

// 尝试直接调用私有或保护方法会报错
// $processor->validateInput("test"); // Fatal error: Call to private method
// $processor->applyBusinessLogic("test"); // Fatal error: Call to protected method

$advProcessor = new AdvancedDataProcessor();
echo $advProcessor->extendedProcess("advanced data") . "/n"; // OK

use

// 假设这是某个只有管理员才能调用的函数
function performAdminAction($actionName, $currentUser) {
    if (!isset($currentUser['role']) || $currentUser['role'] !== 'admin') {
        error_log("Unauthorized attempt to perform admin action: " . $actionName);
        return false; // 或者抛出异常
    }
    // 真正的管理员操作逻辑
    echo "Admin action '{$actionName}' performed by {$currentUser['username']}./n";
    return true;
}

// 示例调用
$user1 = ['username' => 'guest', 'role' => 'user'];
$user2 = ['username' => 'john_doe', 'role' => 'admin'];

performAdminAction('delete_user', $user1); // 输出错误日志，返回false
performAdminAction('reset_password', $user2); // 正常执行

<?php include 'config.php'; function myFunc() { ... } ?>

class UserProfile {
    public function displayProfile($userId) {
        // 这是一个公开的方法，外部可以直接调用
        echo "Displaying profile for user ID: " . $userId . "/n";
    }
}

$profile = new UserProfile();
$profile->displayProfile(123); // 外部直接调用，没问题

class DatabaseConnection {
    protected function connect() {
        echo "Connecting to database.../n";
        // 实际的数据库连接逻辑
        return true;
    }

    public function query($sql) {
        if ($this->connect()) { // 类内部调用protected方法
            echo "Executing query: " . $sql . "/n";
            // 执行查询的逻辑
            return ['result' => 'data'];
        }
        return false;
    }
}

class MyRepository extends DatabaseConnection {
    public function fetchData($id) {
        // 子类可以访问protected方法
        if ($this->connect()) {
            echo "Fetching data for ID: " . $id . "/n";
            return $this->query("SELECT * FROM items WHERE id = " . $id);
        }
        return null;
    }
}

$repo = new MyRepository();
$repo->fetchData(456); // OK
// $repo->connect(); // 致命错误：Call to protected method

class OrderProcessor {
    private $orderStatus = 'pending';

    private function generateOrderId() {
        // 这是一个私有方法，只用于本类内部生成订单ID
        $id = uniqid('ORDER_');
        echo "Generated order ID: " . $id . "/n";
        return $id;
    }

    public function createOrder($items) {
        $orderId = $this->generateOrderId(); // 类内部调用私有方法
        echo "Creating order " . $orderId . " with items: " . implode(', ', $items) . "/n";
        $this->orderStatus = 'created';
        return $orderId;
    }
}

class SpecialOrderProcessor extends OrderProcessor {
    // public function testPrivate() {
    //     $this->generateOrderId(); // 致命错误：Call to private method
    // }
}

$processor = new OrderProcessor();
$processor->createOrder(['itemA', 'itemB']); // OK
// $processor->generateOrderId(); // 致命错误：Call to private method

include

require

function createProcessor() {
    $privateData = "Internal secret";

    // 这是一个内部辅助函数，外部无法直接调用
    $internalHelper = function($param) use ($privateData) {
        echo "Internal helper processing: " . $param . " with " . $privateData . "/n";
        return strtoupper($param);
    };

    // 返回一个公共接口
    return function($input) use ($internalHelper) {
        if (strlen($input) < 3) {
            return "Input too short!";
        }
        return $internalHelper($input); // 内部调用私有辅助函数
    };
}

$processor = createProcessor();
echo $processor("hello") . "/n"; // OK
echo $processor("hi") . "/n"; // Input too short!

// 外部无法访问 $internalHelper
// $processor->internalHelper("test"); // 报错，因为 $processor 只是一个闭包，没有这个方法