观察者模式

1 <?php 2     //定义观察者调用接口 3     class transfer{ 4         protected $_observers = array(); 5          6         //注册对象 7         public function register($sub){ 8             $this->_observers[] = $sub;     9         }10         11         //外部统一调用12         public function trigger(){13             if(!empty($this->_observers)){14                 foreach($this->_observers as $observer){15                     $observer->update();16                 }    17             }18         }19     }20     21     //观察者接口22     interface obserable{23         public function update();24     }25     26     //实现观察者27     class listen implements obserable{28         public function update(){29             echo 'now first time you need to do listen<br/>';30         }31     }32     33     class read implements obserable{34         public function update(){35             echo 'now first time you need to read<br/>';36         }37     }38     39     class speak implements obserable{40         public function update(){41             echo 'now first time you need to speak<br/>';42         }43     }44     45     class write implements obserable{46         public function update(){47             echo 'now first time you need to write<br/>';48         }49     }50     51     $transfer = new transfer();52     $transfer->register(new listen());53     $transfer->register(new read());54     $transfer->register(new speak());55     $transfer->register(new write());56     $transfer->trigger();