如何在PHP中實現基於主題的發布-訂閱模式

class Subject {
    private $subscribers = [];

    public function subscribe($subscriber) {
        $this->subscribers[] = $subscriber;
    }

    public function unsubscribe($subscriber) {
        $key = array_search($subscriber, $this->subscribers);
        if ($key !== false) {
            unset($this->subscribers[$key]);
        }
    }

    public function publish($message) {
        foreach ($this->subscribers as $subscriber) {
            $subscriber->handleMessage($message);
        }
    }
}

interface Subscriber {
    public function handleMessage($message);
}

class EmailSubscriber implements Subscriber {
    public function handleMessage($message) {
        echo "邮件订阅者收到消息：$message
";
    }
}

class SmsSubscriber implements Subscriber {
    public function handleMessage($message) {
        echo "短信订阅者收到消息：$message
";
    }
}

// 创建主题对象
$subject = new Subject();

// 创建订阅者对象
$emailSubscriber = new EmailSubscriber();
$smsSubscriber = new SmsSubscriber();

// 注册订阅者到主题对象
$subject->subscribe($emailSubscriber);
$subject->subscribe($smsSubscriber);

// 发布消息
$subject->publish("新消息");

// 取消订阅
$subject->unsubscribe($emailSubscriber);

// 再次发布消息
$subject->publish("另一条消息");

邮件订阅者收到消息：新消息
短信订阅者收到消息：新消息
短信订阅者收到消息：另一条消息