function login($username, $password)
{
    $query = $this->db->select('*')
                      ->from('TBL_USER')
                      ->where('USERNAME', $username)
                      ->where('PASSWORD', $password)
                      ->get();

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

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

class VerifyLogin extends CI_Controller {

function __construct()
{
    parent::__construct();
    $this->load->model('m_sisip','',TRUE);
    $this->load->helper(array('form','html'));
    $this->load->library(array('form_validation','session','security'));
}

function index()
{
    $this->load->library('form_validation');

    $this->form_validation->set_rules('username', 'username', 'trim|required|xss_clean');
    $this->form_validation->set_rules('password', 'password', 'trim|required|xss_clean|callback_check_database');

    if($this->form_validation->run() == FALSE)
    {
        $data['base_url'] = $this->config->item('base_url');
        $this->load->view('login',$data);
    }
    else
    {
        redirect('c_ta/index', 'refresh');
    }

}

function check_database($password)
{
    $username = $this->input->post('username');
    $username = $this->security->xss_clean($username);
    $password = $this->input->post('password');
    $password = $this->security->xss_clean($password);

    $result = $this->m_sisip->login($username, $password);

    if($result)
    {

        $sess_array = array();
        foreach($result as $rows)
        {
              $newdata = array(
                  'id_user'     => $rows->ID_USER,
                  'id_role'     => $rows->ID_ROLE,
                  'username'    => $rows->USERNAME,
                  'password'     => $rows->PASSWORD,
                  'nama_user'   => $rows->NAMA_USER,
                  'jenis_kelamin'=> $rows->JENIS_KELAMIN,
                  'alamat_user' => $rows->ALAMAT_USER,
                  'notelp_user' => $rows->NOTELP_USER,
                  'email_user' => $rows->EMAIL_USER,
                  'foto_user' => $rows->FOTO_USER,
                  'is_deleted' => $rows->IS_DELETED,
                  'logged_in' => true
                  );
        }

         $this->session->set_userdata($newdata);
         return true;
    }
    else
    {
         $this->form_validation->set_message('check_database', 'invalid username or password');
         return false;
     }
 }
}
?>

<form action="<?php echo site_url('verifylogin');?>"method="POST">
        <fieldset>
            <label class="block clearfix">
                <span class="block input-icon input-icon-right">
                    <input type="text" id="username" name="username" class="form-control" placeholder="Username" />
                    <i class="ace-icon fa fa-user"></i>
                </span>
            </label>

            <label class="block clearfix">
                <span class="block input-icon input-icon-right">
                    <input type="password" id="password" name="password" class="form-control" placeholder="Password" />
                        <i class="ace-icon fa fa-lock"></i>
                </span>
            </label>

            <div class="space"></div>

            <div class="clearfix">
                <div class="text-center">
                    <button type="submit" class="width-35 pull-justify btn btn-sm btn-danger">
                      <i class="ace-icon fa fa-key"></i>
                        <span class="bigger-110">Login</span>
                    </button>
                </div>
            </div>
            <div class="space-4"></div>
       </fieldset>
       </form>