observer模式

<?php

/**
 * @来自 http://www.php.net/manual/en/class.splobserver.php
 * 报纸
 * 观察者模式中的主体
 * 使用了spl中的观察者模式的接口，so php>=5.3
 * 整理: 苏小林
 */
class Newspaper implements SplSubject{
    private $name;
    private $observers = array();
    private $content;
    
    public function __construct($name) {
        $this->name = $name;
    }

    //添加一个观察者
    public function attach(SplObserver $observer) {
        $this->observers[] = $observer;
    }
    
    //删除一个观察者
    public function detach(SplObserver $observer) {
        //获取待删除的观察者所在的键
        $key = array_search($observer,$this->observers, true);
        if($key){
            //删除指定观察者
            unset($this->observers[$key]);
        }
    }
    
    //发生了突发新闻
    public function breakOutNews($content) {
        $this->content = $content;
        //通知观察者，调用主体的notify方法
        $this->notify();
    }
    
    public function getContent() {
        return $this->content." ({$this->name})";
    }
    
    //通知所有观察者(或者可以选择性的通知某些观察者)
    public function notify() {
        foreach ($this->observers as $value) {
            $value->update($this);
        }
    }
}

/**
 * 收到主体通知的观察者
 */
class Reader implements SplObserver{
    private $name;
    
    public function __construct($name) {
        $this->name = $name;
    }
    
    //收到新闻后的动作，参数为主体对象
    public function update(SplSubject $subject) {
        echo $this->name." is reading breakout news <b>".$subject->getContent()."</b>
";
    }
}

//主体(报纸)
$newspaper = new Newspaper("Newyork Times");

$allen = new Reader("Allen");
$jim = new Reader("Jim");
$linda = new Reader("Linda");

//保存添加观察者到主体中(读者)
$newspaper->attach($allen);
$newspaper->attach($jim);
$newspaper->attach($linda);

//从主体中删除指定的观察者
$newspaper->detach($linda);

//发布一个突发新闻(触发观察者的行为)
$newspaper->breakOutNews("USA break down!");

//=====输出======
//Allen is reading breakout news USA break down! (Newyork Times)
//Jim is reading breakout news USA break down! (Newyork Times)