PHP 设计模式在容器和微服务架构中的应用

// 数据库连接单例类
class Database
{
    private static $instance = null;

    private function __construct() {}

    public static function getInstance()
    {
        if (self::$instance === null) {
            self::$instance = new PDO('mysql:host=localhost;dbname=db', 'root', 'password');
        }

        return self::$instance;
    }
}

// 获取数据库连接实例
$db = Database::getInstance();

// 事件接口
interface EventInterface
{
    public function getName();
}

// 事件类
class UserCreatedEvent implements EventInterface
{
    private $userId;

    public function __construct(int $userId)
    {
        $this->userId = $userId;
    }

    public function getName()
    {
        return 'user_created';
    }
}

// 观察者类
class NotifierObserver
{
    public function notify(EventInterface $event)
    {
        // 发送通知...
    }
}

// 事件发布者
class EventPublisher
{
    private $observers = [];

    public function subscribe(ObserverInterface $observer)
    {
        $this->observers[] = $observer;
    }

    public function publish(EventInterface $event)
    {
        foreach ($this->observers as $observer) {
            $observer->notify($event);
        }
    }
}