Session class you are required to set an encryption key

[eluser]davy_yg[/eluser]

Hello,

I have this codes:

Code:

<?php

class Login extends CI_Controller {

function index()
{
  $data['main_content'] = 'login_form';
  $this->load->view('includes/template', $data);
}

function validate_credentials()
{
  $this->load->model('membership_model');
  $query = $this->membership_model->validate();

  if($query) // user's credential validated..
  {
   $data = array(
    'username' => $this->input->post('username'),
    'is_logged_in' => true
   );
  
   $this->session->set_userdata('data');
   redirect('site/members_area');
  }

  else
  {
   $this->index();  
  }
  

}

}


?>

and I receive this error:

An Error Was Encountered

In order to use the Session class you are required to set an encryption key in your config file.

How to fix this problem?