<?php//使用接口，类必须实现几个功能注册，删除，通知这几个动作interface Subject{	public function registerObserver(Observer $o);	public function removeObserver(Observer $o);	public function notifyObservers();}interface Observer{	public function update($a,$b,$c);}//各个面板不同将改行为以接口实现interface DisplayElement{	public function display();}class Weather implements Subject{	public $observers;	public $changed=false;	public $a;	public $b;	public $c;	public function __construct(){		$this->observers = array();	}	public function registerObserver(Observer $o){		$this->observers[] = $o;	}	public function removeObserver(Observer $o){		$key = array_search($o,$this->observers);		if($key!==false){			unset($this->observers[$key]);		}	}	public function notifyObserver(){		if($this->changed){			foreach($this->observer as $ob){				$ob->update($this->a,$this->b,$this->c);			}		}	}	public function setChanged(){		$this->changed = true;	}	//当数值改变时通知各个观察者	public function measurementsChanged(){		$this->setChanged();		$this->notifyObserver();	}	public function setMeasurements($a,$b,$c){		$this->a = $a;		$this->b = $b;		$this->c = $c;		$this->measurementsChanged();			}}class CurrentConditionsDisplay implements Observer, DisplayElement{	public $a;	public $b;	public $c;	public $subject;	public function __construct(Subject $weather){		$this->subject = $weather;		$this->subject->registerObserver($this);	}	public function update($a,$b,$c){		$this->a = $a;		$this->b = $b;		$this->c = $c;		$this->display();	}	public function display(){		echo $this->a.$this->b.$this->c;	}}?>