PHP观察者模式示例【Laravel框架中有用到】

<?php
//观察者模式
//抽象主题类
interface Subject
{
  public function attach(Observer $Observer);
  public function detach(Observer $observer);
  //通知所有注册过的观察者对象
  public function notifyObservers();
}
//具体主题角色
class ConcreteSubject implements Subject
{
  private $_observers;
  public function __construct()
  {
    $this->_observers = array();
  }
  //增加一个观察者对象
  public function attach(Observer $observer)
  {
    return array_push($this->_observers,$observer);
  }
  //删除一个已经注册过的观察者对象
  public function detach(Observer $observer)
  {
    $index = array_search($observer,$this->_observers);
    if($index === false || !array_key_exists($index, $this->_observers)) return false;
    unset($this->_observers[$index]);
    return true;
  }
  //通知所有注册过的观察者
  public function notifyObservers()
  {
    if(!is_array($this->_observers)) return false;
    foreach($this->_observers as $observer)
    {
      $observer->update();
    }
    return true;
  }
}
//抽象观察者角色
interface Observer
{
  //更新方法
  public function update();
}
//观察者实现
class ConcreteObserver implements Observer
{
  private $_name;
  public function __construct($name)
  {
    $this->_name = $name;
  }
  //更新方法
  public function update()
  {
    echo 'Observer'.$this->_name.' has notify';
  }
}
$Subject = new ConcreteSubject();
//添加第一个观察者
$observer1 = new ConcreteObserver('baixiaoshi');
$Subject->attach($observer1);
echo 'the first notify:';
$Subject->notifyObservers();
//添加第二个观察者
$observer2 = new ConcreteObserver('hurong');
echo '<br/>second notify:';
$Subject->attach($observer2);
/*echo $Subject->notifyObservers();
echo '<br/>';
$Subject->notifyObservers();*/
?>