ThinkPHP3.2.3调用全局控制器导致网页重复输出是什么原因？

（1）全局控制器，路径"Apps/Common/Controller/BaseController.class.php"
namespace Common\Controller;
use Think\Controller;
class BaseController extends Controller {
public function _initialize(){
//调用数据库代码省略
$this -> assign(...);
$this -> display();
}
}
?>
（2）模块控制器，路径"Apps/Home/Common/Controller/HomeController.class.php"
namespace Home\Common\Controller;
use Common\Controller\BaseController;
class HomeController extends BaseController {
}
?>
（3）局部控制器，路径"Apps/Home/Controller/IndexController.class.php"
namespace Home\Controller;
use Home\Common\Controller\HomeController;
class IndexController extends HomeController {
public function index(){
$this -> display();
}
}
?>

输出到模板时，网页出现了重复，就是