没报错但是取不到值，只能打印出 学习

Question

<?php

namespace app\index\controller;
use think\Controller;
class Test1 extends Controller
{
   public function index(){
       return 'shepi';
   }
   public function demo3()
   {
       return '学习'.$this->request->param('lesson');
   }
   public function demo4()
   {
       return '学习'.$this->request->get('lesson');
       //return '学习'.Request::instance()->param('lesson');
   }
}