<?php//觀察者模式//抽象主題類interface Subject{  public function attach(Observer $Observer);  public function detach(Observer $observer);  //通知所有注冊過的觀察者對象  public function notifyObservers();}//具體主題角色class ConcreteSubject implements Subject{  private $_observers;  public function __construct()  {    $this->_observers = array();  }  //增加一個觀察者對象  public function attach(Observer $observer)  {    return array_push($this->_observers,$observer);  }  //刪除一個已經注冊過的觀察者對象  public function detach(Observer $observer)  {    $index = array_search($observer,$this->_observers);    if($index === false || !array_key_exists($index, $this->_observers)) return false;    unset($this->_observers[$index]);    return true;  }  //通知所有注冊過的觀察者  public function notifyObservers()  {    if(!is_array($this->_observers)) return false;    foreach($this->_observers as $observer)    {      $observer->update();    }    return true;  }}//抽象觀察者角色interface Observer{  //更新方法  public function update();}//觀察者實現class ConcreteObserver implements Observer{  private $_name;  public function __construct($name)  {    $this->_name = $name;  }  //更新方法  public function update()  {    echo 'Observer'.$this->_name.' has notify';  }}$Subject = new ConcreteSubject();//添加第一個觀察者$observer1 = new ConcreteObserver('baixiaoshi');$Subject->attach($observer1);echo 'the first notify:';$Subject->notifyObservers();//添加第二個觀察者$observer2 = new ConcreteObserver('hurong');echo '<br/>second notify:';$Subject->attach($observer2);/*echo $Subject->notifyObservers();echo '<br/>';$Subject->notifyObservers();*/?>