delete_cookie()

[eluser]ci_user[/eluser]
I'm trying to delete cookies on logout without success... any suggestions? My code is:

Code:

function logout(){
  $this->load->helper('cookie');
  delete_cookie('csrf_cookie_security');
  delete_cookie('anothercookie');
  $this->session->sess_destroy();
  $this->output->set_header("Cache-Control: no-store, no-cache, must-revalidate, no-transform, max-age=0, post-check=0, pre-check=0");
  $this->output->set_header("Pragma: no-cache");
}