PHP设计模式观察者模式

//抽象通知者
abstract class Subject
{
    private $observers = array();

    public function  Attach(Observer $observer)
    {
        array_push($this->observers,$observer);
    }

    public function  Detach(Observer $observer)
    {
        foreach($this->observers as $k=>$v)
        {
            if($v==$observer)
            {
                unset($this->observers[$k]);
            }
        }
    }

    function  Notify()
    {
        foreach($this->observers as $v)
        {
            $v->Update();
        }
    }
}

//具体通知者（Boss和Secretary）
class ConcreteSubject extends Subject
{
   public $subject_state;
}

//抽象观察者
abstract class Observer
{
    public abstract function Update();
}

//具体观察者
class ConcreteObserver extends Observer
{
    private $name;
    private $observerState;
    public $subject;

    public function __construct(ConcreteSubject $_sub,$_name)
    {
        $this->subject = $_sub;
        $this->name = $_name;
    }

    public function  Update()
    {
        $this->observerState = $this->subject->subject_state;
        echo 观察者.$this->name.的新状态是:.$this->observerState.
;
    }
}

header(Content-Type:text/html;charset=utf-8);
//-------------------------观察者模式-----------------------
require_once ./Observe/Observe.php;
//前台
$_s = new ConcreteSubject();

//宝银
$baoyin = new ConcreteObserver($_s, 张三);
$jiangchao = new ConcreteObserver($_s,李四);

//前台记下宝银姜超
$_s->Attach($baoyin);
$_s->Attach($jiangchao);

//前台发现老板回来
$_s->subject_state = 孙总回来了;

//前台发送通知
$_s->Notify();