一个很基础的单例模式的SESSION管理类

start_session();
        return self::$instance;
    }
 
    public function start_session(){
        if($this->session_state == self::SESSION_NOT_STARTED){
            $this->session_state = session_start();
        }
        return $this->session_state;
    }
 
    public function __set($name,$value){
        $_SESSION[$name] = $value;
    }
 
    public function __get($name){
        if(isset($_SESSION[$name])){
            return $_SESSION[$name];
        }
    }
 
    public function __isset($name){
        return isset($_SESSION[$name]);
    }
 
    public function __unsset($name){
        unset($_SESSION[$name]);
    }
 
    public function destroy(){
        if($this->session_state == self::SESSION_STARTED){
            $this->session_state = !session_destroy();
            unset($_SESSION);
            return !$this->session_state;
        }
 
        return false;
    }
}