php實現觀察者模式

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<meta charset=‘utf-8‘ /><title>觀察者模式</title><?php    class Tongzhi implements SPLSubject    {        protected $subs = array();        public $username = ‘我是被觀察者‘;        public function __construct(){        }                public function attach(SPLObserver $sub){            $this->subs[] = $sub;        }        public function detach(SPLObserver $sub){            $keys = array_keys($this->subs,$sub);            $key = $keys[0];            unset($this->subs[$key]);        }        public function notify(){            foreach ($this->subs as $value)             {                $value->update($this);            }        }    }    class Obs1 implements SPLObserver    {        public function update(SPLSubject $tz){            echo $tz->username.‘，我是觀察者1<br />‘;        }    }    class Obs2 implements SPLObserver    {        public function update(SPLSubject $tz){            echo $tz->username.‘，我是觀察者2<br />‘;        }    }    class Obs3 implements SPLObserver    {        public function update(SPLSubject $tz){            echo $tz->username.‘，我是觀察者3<br />‘;        }    }    $tz = new Tongzhi;    $tz->attach(new Obs1);    $tz->attach(new Obs2);    $tz->detach(new Obs2);    $tz->attach(new Obs3);    $tz->notify();?>

php實現觀察者模式