set_message callback

[eluser]Unknown[/eluser]
Hello, I don't knot why, this message: $this->form_validation->set_message('validate_credentials', 'incorrect !!'); is not displayed when I entered wrong data.

Code:

public function login()
{
    $d['v'] = 'login';
   $this->load->view('initiator', $d);
}
public function members()
{
  $this->load->view('members');
}

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

  $this->form_validation->set_rules('login', 'Login', 'required|trim|callback_validate_credentials');
  $this->form_validation->set_rules('password', 'Pass', 'required|md5|trim');
  $this->form_validation->set_message('required', 'Pole %s jest wymagane !!');

  if($this->form_validation->run())
  {
   redirect('kontroller/members');
  }
  else
  {
   $this->load->view('login');
  }
}

public function validate_credentials()
{
  $this->load->model('users_m');
  if($this->users_m->can_log_in()){
   return true;
  }
  else
  {
   $this->form_validation->set_message('validate_credentials', 'incorrect !!');
   return false;
  }
}

login.php

Code:

<?php echo form_open('','class="form-horizontal"'); ?>
  <?php if (validation_errors()): ?>
<div class="alert alert-danger">&lt;?php echo validation_errors(); ?&gt;</div>
&lt;?php endif; ?&gt;
  <div class="form-group">
    <label for="login" class="col-sm-2 control-label">Login</label>
    <div class="col-sm-4">
      &lt;?php echo form_input('login', '', 'class="form-control" id="login" placeholder="Login"'); ?&gt;
    </div>
  </div>

  <div class="form-group">
    <label for="password" class="col-sm-2 control-label">Password</label>
    <div class="col-sm-4">
      &lt;?php echo form_password('password', '', 'class="form-control" id="password" placeholder="Hasło"'); ?&gt;
    </div>
  </div>

  <div class="form-group">
    <div class="col-sm-offset-2 col-sm-10">
  
      &lt;?php echo form_submit('login_sumbit', 'Zaloguj!', 'class="btn btn-default"'); ?&gt;
    </div>
  </div>
   &lt;?php echo form_close();?&gt;

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

class Users_m extends CI_Controller {

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

public function insert($table, $data)
{
$this->db->insert($table, $data);
}

public function can_log_in()
{
$this->db->where('login', $this->input->post('login'));
$this->db->where('password', md5($this->input->post('password')));

$query = $this->db->get('users');

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

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