Login session sederhana CodeIgniter3

Auth.php

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

class Auth extends CI_Controller {

  public function __construct()
  {
    parent::__construct();
    $this->load->model('model_login');
  }

  public function login()
  {
    if (isset($_POST['submit'])) {
      # proses login disini
      # ambil data inputan (user & pass) dari form
      $username = $this->input->post('username');
      $password = $this->input->post('password');
      # cek data input ada/tidak pada DB
      $tes = $this->model_login->login($username,$password);
      if ($tes==1) {
        # jika data ditemukan set session & redirect ke home
        $data = array(
          'status_login' => 'oke',
          'username' => $username
        );
        
        $this->session->set_userdata($data);
        redirect('home','refresh');
      } else {
        # jika data tidak ditemukan kembali ke form login
        redirect('auth/login','refresh');
      }
    } else {
      # cek session login, jika session sebelumnya masih ada/tidak
      cek_session_login();
      $this->load->view('form_login');
    }
  }

  public function logout()
  {
    # mengakhiri session, dan redirect ke form_login
    $this->session->sess_destroy();
    redirect('auth/login','refresh');
  }

}

/* End of file auth.php */
/* Location: ./application/controllers/auth.php */

autoload.php

<?php  if ( ! defined('BASEPATH')) exit('No direct script access allowed');
/*
| -------------------------------------------------------------------
| AUTO-LOADER
| -------------------------------------------------------------------
| This file specifies which systems should be loaded by default.
|
| In order to keep the framework as light-weight as possible only the
| absolute minimal resources are loaded by default. For example,
| the database is not connected to automatically since no assumption
| is made regarding whether you intend to use it.  This file lets
| you globally define which systems you would like loaded with every
| request.
|
| -------------------------------------------------------------------
| Instructions
| -------------------------------------------------------------------
|
| These are the things you can load automatically:
|
| 1. Packages
| 2. Libraries
| 3. Helper files
| 4. Custom config files
| 5. Language files
| 6. Models
|
*/

/*
| -------------------------------------------------------------------
|  Auto-load Packges
| -------------------------------------------------------------------
| Prototype:
|
|  $autoload['packages'] = array(APPPATH.'third_party', '/usr/local/shared');
|
*/

$autoload['packages'] = array();


/*
| -------------------------------------------------------------------
|  Auto-load Libraries
| -------------------------------------------------------------------
| These are the classes located in the system/libraries folder
| or in your application/libraries folder.
|
| Prototype:
|
|	$autoload['libraries'] = array('database', 'session', 'xmlrpc');
*/

$autoload['libraries'] = array('session','database');


/*
| -------------------------------------------------------------------
|  Auto-load Helper Files
| -------------------------------------------------------------------
| Prototype:
|
|	$autoload['helper'] = array('url', 'file');
*/

$autoload['helper'] = array('url','form','login');


/*
| -------------------------------------------------------------------
|  Auto-load Config files
| -------------------------------------------------------------------
| Prototype:
|
|	$autoload['config'] = array('config1', 'config2');
|
| NOTE: This item is intended for use ONLY if you have created custom
| config files.  Otherwise, leave it blank.
|
*/

$autoload['config'] = array();


/*
| -------------------------------------------------------------------
|  Auto-load Language files
| -------------------------------------------------------------------
| Prototype:
|
|	$autoload['language'] = array('lang1', 'lang2');
|
| NOTE: Do not include the "_lang" part of your file.  For example
| "codeigniter_lang.php" would be referenced as array('codeigniter');
|
*/

$autoload['language'] = array();


/*
| -------------------------------------------------------------------
|  Auto-load Models
| -------------------------------------------------------------------
| Prototype:
|
|	$autoload['model'] = array('model1', 'model2');
|
*/

$autoload['model'] = array();


/* End of file autoload.php */
/* Location: ./application/config/autoload.php */

form_login.php

<?=form_open('auth/login');?>
  <table>
    <tr><td>Username</td><td><input type="text" name="username"></td></tr>
    <tr><td>Password</td><td><input type="password" name="password"></td></tr>
    <tr><td colspan="2" align="center"><button type="submit" name="submit">LOGIN</button></td></tr>
  </table>
<?=form_close();?>

Home.php

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

class Home extends CI_Controller {

  public function index()
  {
    # cek kembali session, jika blm login di redirect lagi ke form login
    cek_session();
    $this->load->view('v_home');
  }

}

/* End of file home.php */
/* Location: ./application/controllers/home.php */

login_helper.php

<?php
function cek_session()
{
  $CI =& get_instance();
  $session = $CI->session->userdata('status_login');
  if ($session!='oke') {
    # jika status_login tidak sesuai kriteria
    redirect('auth/login','refresh');
  }
}


function cek_session_login()
{
  $CI =& get_instance();
  $session = $CI->session->userdata('status_login');
  if ($session=='oke') {
    # jika status_login sesuai kriteria
    redirect('home','refresh');
  }
}

/* End of file login_helper.php */
/* Location: ./application/helpers/login_helper.php */

Model_login.php

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

class Model_login extends CI_Model {

  function login($username,$password)
  {
    $val = array(
      'username' => $username,
      'password' => md5($password)
      );

    # cek apakah data dari form ada/tidak di DB
    $cek = $this->db->get_where('t_user', $val);
    if ($cek->num_rows()>0) {
      # jika data ada
      return 1;
    } else {
      # jika data tidak ada
      return 0;
    }
  }

}

/* End of file model_login.php */
/* Location: ./application/models/model_login.php */

t_user.sql

CREATE TABLE IF NOT EXISTS `t_user` (
`user_id` int(11) NOT NULL PRIMARY KEY AUTO_INCREMENT,
  `nama_lengkap` varchar(40) NOT NULL,
  `username` varchar(20) NOT NULL,
  `password` varchar(32) NOT NULL,
);

v_home.php

<h1>Halaman Home</h1>
<p>Link : <?=anchor('auth/logout', 'Logout');?></p>