解析PHP观察者模式Observer

// 主题接口
interface Subject{
    public function register(Observer $observer);
    public function notify();
}
// 观察者接口
interface Observer{
    public function watch();
}

// 被观察者
class Action implements Subject{
     public $_observers=array();
     public function register(Observer $observer){
         $this->_observers[]=$observer;
     }
 
     public function notify(){
         foreach ($this->_observers as $observer) {
             $observer->watch();
         }
 
     }
 }

// 观察者
class Cat implements Observer{
     public function watch(){
         echo "Cat watches TV<hr/>";
     }
 }
 class Dog implements Observer{
     public function watch(){
         echo "Dog watches TV<hr/>";
     }
 }
 class People implements Observer{
     public function watch(){
         echo "People watches TV<hr/>";
     }
 }

// 应用实例
$action=new Action();
$action->register(new Cat());
$action->register(new People());
$action->register(new Dog());
$action->notify();

class user{

  public function login()
  {
      echo '登录完毕'
  }

class user implements splsubject{

    protected $observer = null;

    public function __construct()
    {
        $this->observer = new SplObjectStorage();
    }

    public function login()
    {
        $this->notify();
        echo '登录完毕';
    }

    public function attach(SplObserver $observer)
    {
        $this->observer->attach($observer);
    }

    public function detach(SplObserver $observer)
    {
        $this->observer->detach($observer);
    }

    public function notify()
    {
        $this->observer->rewind();
        while ($this->observer->valid())
        {
            $observer = $this->observer->current();
            $observer->update($this);
            $this->observer->next();
        }
    }
}

class cat implements SplObserver {

    public function update(SplSubject $subject)
    {
        echo '小猫叫一下';
    }
}
class dog implements SplObserver {
    public function update(SplSubject $subject)
    {
        echo '小狗吼一声';
    }
}

// 实时观察
$user = new user();
$user->attach(new cat());
$user->attach(new dog());
$user->login();