Codeigniter จะส่งตัวแปรไปอีกหน้าแต่ขึ้น severity notice message undefined variable

<?php
defined('BASEPATH') OR exit('No direct script access allowed');

class Login extends CI_Controller { //ชื่อ class กับชื่อไฟล์ควรเป็นชื่อเดียวกัน

	public function index() {
		$this->load->view('login'); //ส่งไปแสดงผลที่ views/login.php
	}

	public function CheckLogin() {
		$this->form_validation->set_rules('username', 'Username', 'required|trim', array('required'=>'กรุณากรอกชื่อผู้ใช้')); //ฟิลด์, label
		$this->form_validation->set_rules('password', 'Password', 'required|trim|callback_verifyUser', array('required'=>'กรุณากรอกรหัสผ่าน'));
                $this->form_validation->set_error_delimiters('<p class="text-danger">', '</p>');
                
		if ($this->form_validation->run() == false) {
			$this->load->view('login');
		}
		else {
			redirect('Home','refresh');
		}
	}

	public function verifyUser($password) {
                $username = $this->input->post('username');

		$this->load->model('LoginModel'); // เรียกใช้งาน LoginModel
                $result = $this->LoginModel->login($username, $password); //query the database ส่งค่าไปที่ LoginModel
                
		if ($result) {
                    $sess_array = array();
                    //if(isset($result) && sizeof($result)>0){ 
                         foreach($result as $row){ 
                            $sess_array = array(
                                'username'=>$row->uLogin, // ชื่อsession=>$row->ฟิลด์
                                'level'=>$row->uLevel
                            );
                            $this->session->set_userdata('logged_in', $sess_array); //สร้าง session จากตัวแปร array
                        }
                    //}  
                    return true;
		}
		else {
			$this->form_validation->set_message('verifyUser', 'ชื่อผู้ใช้หรือรหัสผ่านผิด! กรุณาลองอีกครั้ง');
                    return false;
		}
	}
}

<?php 
    if ( ! defined('BASEPATH')) exit('No direct script access allowed');
    //session_start(); //we need to call PHP's session object to access it through CI

    class Home extends CI_Controller {
       
        public function index() {
            if($this->session->userdata('logged_in') == null){ 
                $this->load->view('login');
            }
            else {
                $this->load->view('index');
            }
                print_r($this->session->userdata('logged_in'));
	}
        
        public function sess(){
            if($this->session->userdata('logged_in')){
                $session_data = $this->session->userdata('logged_in');
                $data['username'] = $session_data['username'];
                $data['level'] = $session_data['level'];
                    $this->load->view('home', $data);
            }
            else{
                //If no session, redirect to login page
                redirect('login', 'refresh');
            }
        }
 
        public function logout(){
            $this->session->unset_userdata('logged_in');
            session_destroy();
            redirect('login', 'refresh');
        }
    }
?>

<?php
defined('BASEPATH') OR exit('No direct script access allowed');

	class LoginModel extends CI_Model
	{
		public function login($name,$pass) 
		{
			$this->db->select('uLogin','uPassword','uLevel');
			$this->db->from('tbl_user');
			$this->db->where('uLogin', $name);
			$this->db->where('uPassword', md5($pass));

			$query = $this->db->get();

			if ($query->num_rows() == 1) {
				return $query->result();
			}
			else {
				return false;
			}
		}
	}
?>

<h1>หน้าหลัก !</h1><?php echo $username; ?>
        <a href="<?php echo base_url() ?>index.php/home/logout">Logout</a>