PHP实现的观察者模式实例

<?php  //定义观察者调用接口  class transfer{    protected $_observers = array();    //注册对象    public function register($sub){      $this->_observers[] = $sub;    }    //外部统一调用    public function trigger(){      if(!empty($this->_observers)){        foreach($this->_observers as $observer){          $observer->update();        }      }    }  }  //观察者接口  interface obserable{    public function update();  }  //实现观察者  class listen implements obserable{    public function update(){      echo 'now first time you need to do listen<br/>';    }  }  class read implements obserable{    public function update(){      echo 'now first time you need to read<br/>';    }  }  class speak implements obserable{    public function update(){      echo 'now first time you need to speak<br/>';    }  }  class write implements obserable{    public function update(){      echo 'now first time you need to write<br/>';    }  }  $transfer = new transfer();  $transfer->register(new listen());  $transfer->register(new read());  $transfer->register(new speak());  $transfer->register(new write());  $transfer->trigger();