php设计模式Observer(观察者模式)

_observers[] = $observer;
    }
    public function removeObserver($observer) {
        $key = array_search($observer, $this->_observers);
        if (!($key === false)) {
            unset($this->_observers[$key]);
        }
    }
    public function notifyObservers() {
        foreach ($this->_observers as $observer) {
            if ($observer instanceof Observer) $observer->update($this);
        }
    }
}
interface Observer {
    public function update($observer);
}
interface DisplayElement {
    public function display();
}
// -- 实例类定义
class NewsObserverable extends Observerable {
    private $_sports_news;
    public function setSportsNews($data) {
        $this->_sports_news = $data;
        $this->notifyObservers();
    }
    public function getSportsNews() {
        return $this->_sports_news;
    }
    private $_local_news;
    public function setLocalNews($data) {
        $this->_local_news = $data;
        $this->notifyObservers();
    }
    public function getLocalNews() {
        return $this->_local_news;
    }
}
class SportsNews implements Observer, DisplayElement {
    private $_data = null;
    public function update($observer) {
        if ($this->_data != $observer->getSportsNews()) {
            $this->_data = $observer->getSportsNews();
            $this->display();
        }
    }
    public function display() {
        echo $this->_data . date("Y-m-d H:i:s") . "
";
    }
}
class LocalNews implements Observer, DisplayElement {
    private $_data = null;
    public function update($observer) {
        if ($this->_data != $observer->getLocalNews()) {
            $this->_data = $observer->getLocalNews();
            $this->display();
        }
    }
    public function display() {
        echo $this->_data . date("Y-m-d H:i:s") . "
";
    }
}
// -- 实例化 ---
$objObserver = new NewsObserverable();
$local = new LocalNews();
$sports = new SportsNews();
$objObserver->registerObserver($local);
$objObserver->registerObserver($sports);
$objObserver->setSportsNews("sports news 1 ");
$objObserver->setLocalNews("local news 1 ");
$objObserver->removeObserver($sports);
$objObserver->setLocalNews("local news 2 ");
$objObserver->setSportsNews("sports news 2 ");
$objObserver->removeObserver($local);
$objObserver->setLocalNews("local news 3 ");

其他相关设计模式：

备忘录模式(Memento模式)
观察者模式(Observer模式)
模板方法模式(Template Method模式)
命令模式(command模式)
组合模式(composite模式)
享元模式(flyweight模式)
策略模式(strategy模式)
状态模式(state模式)
适配器模式(adapter模式)
工厂模式(factory模式)
原型模式(prototype模式)
外观模式(facade模式)
单例模式(singleton模式)
桥梁模式(bridge模式)
装饰模式(decorator模式)
抽象工厂模式(abstract factory模式)
建造者模式(Builder模式)
访问者模式(Visitor模式)
解释器模式(Interpreter模式)
中介者模式(Mediator模式)
职责链模式(Chain Of Responsibility模式)
代理模式(Proxy模式)
迭代器模式(Interator模式)
数据访问对象模式(DAO模式)
委托模式(Delegation模式)