PHP 디자인 패턴 중 관찰자 패턴에 대한 자세한 설명

<?php
/**
 * 观察者模式
 * @author: Mac
 * @date: 2012/02/22
 */

abstract class Pa
{
    private $_observers = array();

    public function register($sub)
    {
    }

    public function trigger()
    {
    }
}

class Paper extends Pa
{ /* 主题    */
    private $_observers = array(); // 存放new的对象

    public function register($sub)
    { /*  注册观察者 */
        $this->_observers[] = $sub;
    }


    public function trigger()
    {  /*  外部统一访问    */
        if (!empty($this->_observers)) {
            foreach ($this->_observers as $observer) {
                $observer->update();
            }
        }
    }
}

/**
 * 观察者要实现的接口
 */
interface Observerable
{
    public function update();
}

class Subscriber1 implements Observerable //观察者
{
    public function update()
    {
        echo "观察者1收到执行通知 执行完毕\n";
    }
}

class Subscriber2 implements Observerable //观察者2
{
    public function update()
    {
        echo "观察者2收到执行通知 执行完毕\n";
    }
}


/*  测试    */
$paper = new Paper();
$paper->register(new Subscriber1());
$paper->trigger();