Codeigniter csrf token helper

MY_form_helper.php

// In codeigniter, form_open() can automatic output a csrf token field.
// But, I prefer use the html form tag.
// This function can manually insert a token to form elements.
function csrf_token()
{   
  $CI = & get_instance();
  $hidden[$CI->security->get_csrf_token_name()]= $CI->security->get_csrf_hash();
  $form_token = sprintf("<div style=\"display:none\">%s</div>", form_hidden($hidden));
  echo $form_token;
}