PHP对观察者模式的原生支持

<?php// 观察者模式// PHP(SPL)原生支持/*类摘要SplSubject {	abstract public void attach ( SplObserver $observer );	abstract public void detach ( SplObserver $observer );	abstract public void notify ( void );}SplObserver {	abstract public void update ( SplSubject $subject );}SplObjectStorage implements Countable, Iterator, Serializable, Arrayaccess {} */class ConcreteSubject implements SplSubject{	PRivate $storage;		public function __construct() {		$this->storage = new SplObjectStorage();	}		public function attach(SplObserver $obs) {		$this->storage->attach($obs);	}		public function detach(SplObserver $obs) {		$this->storage->detach($obs);	}		public function notify() {		foreach($this->storage as $ol) {			$ol->update($this);		}	}		public function doAct() {		echo 'DoAct ... <br/>';		$this->notify();	}}/** * concrete observer 1 */class Observer1 implements SplObserver{	public function update(SplSubject $sub) {		echo 'Observer one updated! <br/>';	}}/** * concrete observer 2 */class Observer2 implements SplObserver{	public function update(SplSubject $sub) {		echo 'Observer two updated! <br/>';	}}// test code$sub = new ConcreteSubject();$sub->attach(new Observer1()); //add observer$sub->attach(new Observer1());$sub->attach(new Observer2());$sub->doAct();