Login.php

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

class Login extends CI_Controller {

    /**
     * Index Page for this controller.
     *
     * Maps to the following URL
     *      http://example.com/index.php/welcome
     *  - or -
     *      http://example.com/index.php/welcome/index
     *  - or -
     * Since this controller is set as the default controller in
     * config/routes.php, it's displayed at http://example.com/
     *
     * So any other public methods not prefixed with an underscore will
     * map to /index.php/welcome/<method_name>
     * @see https://codeigniter.com/user_guide/general/urls.html
     */

    /*public function __construct()
    {
        parent::__construct();
    }*/

    public function index()
    {

        $this->load->view('login/index');
    }

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

        $cek = $this->m_login->cek($username,$password);
        if($cek->num_rows()==1)
        {
            foreach ($cek->result() as $data) {
                # code...
                $sess_data['id_username'] = $data->id_username;
                $sess_data['username'] = $data->username;
                $this->session->set_userdata($sess_data);
            }
            redirect('home');
        }
        else
        {
            $this->session->set_flashdata('pesan','Maaf username dan password tidak cocok!');
            redirect('login');
        }
    }

    function keluar()
    {
        $this->session->sess_destroy();
        redirect('login');
    }

}