PHP 觀察者模式

<?php 
/** 
* 觀察者模式 
* 
* 定義對象間的一種一對多的依賴關係,以便當一個對象的狀態發生改變時,所有依賴於它的對象都得到通知並自動刷新 
* 能夠便利地創建查看目標對象狀態的對象,並且提供與核心對象非耦合的指定功能 
* 插件系統 
*/ 
class Observerable {
	private $_observers=array();

	public function registerObserver($observer) {
		$this->_observers[]=$observer;
	}

	public function removeObserver($observer) {
		$key=array_search($observer,$this->_observers);
		if(!($key===false))
		{
			unset($this->_observers[$key]);
		}
	}

	public function notifyObserver() {
		foreach($this->_observers as $key=>$observer)
		{
			if($observer instanceof Observer)
			{
				//$args = func_get_args();
				//call_user_func_array(array($observer,'update'),$this);
				$observer->update($this);
			}
		}
	}
}

interface Observer {
	public function update($observer);
}

class SubjectObserverable extends Observerable {
	private $_subject;
	private $_content;

	public function setSubject($subject) {
		$this->_subject=$subject;
		$this->notifyObserver();
	}

	public function getSubject() {
		return $this->_subject;
	}
}

class KevinObserver implements Observer {
	private $_data=null;

	public function update($observer) {
		$this->_data=$observer->getSubject();
		$this->show();
	}
	
	public function show() {
		echo 'hello Kevin:'.'<br/>';
		var_export($this->_data);
		echo '<br/>';
	}
}

class MarkObserver implements Observer {
	private $_data=null;

	public function update($observer) {
		$this->_data=$observer->getSubject();
		$this->show();
	}
	
	public function show() {
		echo 'hello Mark:'.'<br/>';
		var_export($this->_data);
		echo '<br/>';
	}
}

$oObserverable=new SubjectObserverable();
$oKevin=new KevinObserver();
$oMark=new MarkObserver();

$oObserverable->registerObserver($oKevin);
$oObserverable->registerObserver($oMark);

$oObserverable->setSubject("this is the first subject");

$oObserverable->setSubject("this is the second subject");

$oObserverable->removeObserver($oMark);

$oObserverable->setSubject("this is the third subject");

$oObserverable->removeObserver($oKevin);

$oObserverable->setSubject("this is the fourth subject");