Please help to determine whether the session is logged in!

I would like to ask why my if judgment is not executed!

<if condition="session('uid') eq null"><br>              <a href="__APP__?m=User&a=register" class="menulink">Register Member</a> <br>               <a href="__APP__?m=User&a=login" class="menulink">Member login</a><br>                                                                                                       <a href="__APP__?m=User&a=user" class="menulink">{session('user_name')}</a><br>              </if><br>This is a static page, the controller is written like this if ($result && $result['password'] == $result['password']) {                                                                                                                                              session('uid', $result['user_id']);                    session('user_name', $result['user_name']); // Current username<br>                    session('lastdate', $result['lastdate']); // Last login time<br>                 session('lastip', $result['lastip']);                                                                                                                                                                                         $where['user_id'] = session('uid');<br>                 M('user')->where($where)->setInc('loginnum'); // Add 1 to the number of logins<br>                    M('user')->where($where)->save($data); // Update login time and login ip<br>                       $this->success('Login successful, jumping to the system homepage...', U('Home/User/user'));<br>                } <br>                else {<br>                            $this->error('Login failed, username or password is incorrect!');<br>             }<br>           }<br> <br> <br> 123.jpg <br>( 10.92 KB Download: 0 times )<br>