function index() {

    if ($this->session->userdata('logged_in')) {
        $this->load->view('main');

    } else {
        redirect('/login');
    }
}

function archive() {

    if ($this->session->userdata('logged_in')) {

function __construct()
{
    parent::__construct();
    if ( ! $this->session->userdata('logged_in'))
    {
        // Allow some methods?
        $allowed = array(
            'some_method_in_this_controller',
            'other_method_in_this_controller',
        );
        if ( ! in_array($this->router->fetch_method(), $allowed)
        {
            redirect('login');
        }
    }
}

// Create file application/core/MY_Controller.php
class Auth_Controller extends CI_Controller {

    function __construct()
    {
        parent::__construct();
        if ( ! $this->session->userdata('logged_in'))
        {
            redirect('login');
        }
    }
}

<?php
defined('BASEPATH') OR exit('No direct script access allowed');
class MY_Controller extends CI_Controller {

function __construct()
{
    parent::__construct();
    $CI = & get_instance();
    $CI->load->library('session');
    $CI->load->helper('url');
    if ( !$this->session->userdata('logged_in'))
    {
        redirect('login');
    }
}

function __construct() {
    parent::__construct();
    $CI = & get_instance();
    $CI->load->library('session');
    $CI->load->helper('url');
   // echo "<pre>";print_r($this->router);echo "</pre>";

    /**
     * if webmaster then check admin session else check user session
     * But there may be some classes's method that doesn't requires login hence it is also need to check if
     * current request is for those methods before checking session
     */
    //to use $this->config->item('webmaster_name') this you have to define
    // $config['webmaster_name'] = "webmaster"; in config.php file

    if ($this->router->module == $this->config->item('webmaster_name')) {
        if (!$this->session->userdata('admin')['id']) {
            redirect($this->config->item('webmaster_name').'/login');
        }
    } else {
        if (!$this->session->userdata('user')['id']) {
            redirect('login');
        }
    }
}

function __construct() {
    parent::__construct();
    $CI = & get_instance();
    $CI->load->library('session');
    $CI->load->helper('url');

    //echo "<pre>"; print_r($this->router);echo "</pre>"; //_pr($this->config->item('excluded_auth'));
    /**
     * if webmaster then check admin session else check user session
     * But there may be some classes's method that doesn't requires login hence it is also need to check if
     * current request is for those methods before checking session
     */
    if ($this->router->module == $this->config->item('webmaster_name')) {
        if (!$this->session->userdata('admin')['id']) {
            redirect($this->config->item('webmaster_name') . '/login');
        }
    } else {
        if (array_key_exists($this->router->class, $this->config->item('exclude_auth')) && in_array($this->router->method, $this->config->item('exclude_auth')[$this->router->class])) {
            //echo "escape this method. don not validate for a session";
        } else {
            if (!$this->session->userdata('user')['id']) {
                redirect('login');
            }
        }
    }
}

//save file in application/config/without_auth_methods.php

<?php
     defined('BASEPATH') OR exit('No direct script access allowed');
     $config['exclude_auth']['news']       = array('index', 'view');
     $config['exclude_auth']['users']      = array('index');

protected function isAuthorized()
{

    switch ( strtolower( $this->router->class ) )
    {
        case 'pages':
            $disallowLoggedOut = array( 'dashboard' );
            $disallowLoggedIn = array( 'index' );
        break;

        case 'users':
            $disallowLoggedOut = array( 'logout' );
            $disallowLoggedIn = array( 'register', 'login' );
        break;
    }

    if ( $this->session->userdata( 'loggedIn' ) )
    {
        if ( in_array( $this->router->method, $disallowLoggedIn ) )
        {
            redirect( 'pages/dashboard' );
        }
    }
    else
    {
        if ( in_array( $this->router->method, $disallowLoggedOut ) )
        {
            redirect( 'pages/index' );
        }
    }
}

<?php
 defined('BASEPATH') OR exit('no direct access');

 function isLogin($sessionType)
 {
   if(empty($_SESSION[$sessionType]))
         redirect(base_url('loginURL'));
 }

?>

application/controllers/Access.php

defined('BASEPATH') OR exit('access denied');
class Access Extends CI_Controller
{
  funcrion __construct()
  {
    parent::__construct();
    $this->load->helper('login');
  }
  function home()
  {
    isLogin();
    $this->load->view('home_page);
  }
}