observer观察者模式的PHP实现

用PHP是现在观察者模式。个人觉得观察者模式的重点在于观察者接口以及观察者的注册。以下是代码：

 <?php
2 
3 interface Observer {
4     public function update($time);
5 }
6 
7 ?>

<?php

class Observable {
    private $_observers = array();
    private $_time;
    
    public function registerObserver(Observer $observer) {
        $this->_observers[] = $observer;    
    }
    
    public function removeObserver(Observer $observer) {
        if ($index = array_search($observer, $this->_observers)) {
            unset($this->_observers[$index]);            
        }
    }
    
    public function notifyObservers() {
        foreach ($this->_observers as $observer) {
            $observer->update($this->_time);
        }    
    }
    
    private function _measurementsChanged() {
        $this->notifyObservers();
    }
    
    public function setMeasurements($time) {
        $this->_time = $time;
        $this->_measurementsChanged();    
    }
}

?>

  

 1 <?php
 2 include_once 'Observer.php';
 3 
 4 class ObserverA implements Observer{
 5     public function __construct(Observable $observable) {
 6         $observable->registerObserver($this);
 7     }
 8     
 9     public function update($time) {
10         echo 'ObserverA: received time is '.$time."\r\n";
11     }
12 }
13 
14 ?>

 1 <?php
 2 include_once 'Observer.php';
 3 
 4 class ObserverB implements Observer{
 5     public function __construct(Observable $observable) {
 6         $observable->registerObserver($this);
 7     }
 8     
 9     public function update($time) {
10         echo 'ObserverB: received time is '.$time."\r\n";
11     }
12 }
13 
14 ?>

 1 <?php
 2 include 'Observable.php';
 3 include 'ObserverA.php';
 4 include 'ObserverB.php';
 5 
 6 $observable = new Observable();
 7 
 8 $observerA = new ObserverA($observable);
 9 $observerB = new ObserverB($observable);
10 
11 $observable->setMeasurements('2010-4-4');
12 $observable->setMeasurements('2010-4-5');
13 $observable->setMeasurements('2010-4-10');
14 ?>

 运行结果：