Codeigniter user access level - php

Question

Model:
Class User extends CI_Controller
{
function login($username, $password)
{
$this->db->select('id', 'username', 'password', 'access');
$this->db->from('users');
$this->db->where('username', $username);
$this->db->where('password', MD5($password));
$this->db->limit(1);
$query = $this->db->get();
if($query->num_rows() == 1)
{
return $query->result();
}
else
{
return false;
}
}
}
Controller:
class VerifyLogin extends CI_Controller {
function __construct()
{
parent::__construct();
$this->load->library('form_validation');
$this->load->model('user','',TRUE);
}
function index()
{
$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)
{
//Field validation failed. User redirected to login page
$this->load->view('login_view');
}
else
{
//Go to private area
redirect('home', 'refresh');
}
}
function check_database($password)
{
//Field validation succeeded. Validate against database
$username = $this->input->post('username');
//query the database
$result = $this->user->login($username, $password);
if($result)
{
$sess_array = array();
foreach($result as $row)
{
$sess_array = array(
'id' => $row->id,
'username' => #$row->username
);
$this->session->set_userdata('logged_in', $sess_array);
}
return TRUE;
}
else
{
$this->form_validation->set_message('check_database', 'Invalid username or password');
return false;
}
}
}
How to deal with access? In the database is int number, you need to make a selection from the base, to get the numbers from the table and access to work with him. How to implement it?