设计模式php实例：观察者模式

当一个对象状态发生改变后，会影响到其他几个对象的改变，这时候可以用观察者模式。像wordpress这样的应用程序中，它容外部开发组开发插件，比如用户授权的博客统计插件、积分插件，这时候可以应用观察者模式，先注册这些插件，当用户发布一篇博文后，就回自动通知相应的插件更新。观察者模式符合接口隔离原则，实现了对象之间的松散耦合。观察者模式uml图：在php spl中已经提供splsubject和sqloberver接口[php] view plain copyinterface splsubject  {      function attach(splobserver $observer);      function detach(splobserver $observer);      function notify();  }  interface sqlobserver  {      function update(splsubject $subject);  }  下面具体实现上面例子[php] view plain copyclass subject implements splsubject  {      private $observers;        public function attach(splobserver $observer)      {          if (!in_array($observer, $this->observers)) {              $this->observers[] = $observer;          }      }          public function detach(splobserver $observer)      {          if (false != ($index = array_search($observer, $this->observers))) {              unset($this->observers[$index]);          }      }        public function post()      {          //post相关code          $this->notify();      }        private function notify()      {          foreach ($this->observers as $observer) {              $observer->update($this);          }      }        public function setcount($count)      {          echo "数据量加" . $count;      }      public function setintegral($integral)      {           echo "积分量加" . $integral;      }    }      class observer1 implements splobserver  {      public function update($subject)      {          $subject-> setcount(1);      }  }  class observer2 implements splobserver  {      public function update($subject)      {          $subject-> setintegral(10);      }  }      class client  {      public  function test()      {          $subject = new subject();          $subject->attach(new observer1());          $subject->attach(new observer2());          $subject->post();//输出：数据量加1 积分量加10      }  }