Change the submit handler of a form of a module

Question

I installed base cart module and I need to totally overwrite the submit handler of one of its forms and not to execute its default functionality at all. From what I searched, I wrote this code in template.php :

function ThemeName_form_alter(&$form, &$form_state, $form_id) {
  if ($form_id == 'order_node_form'){
    $form['#submit'] = 'submit';
    $form['#validate'] = '';
  }
}

function submit() {
  return "submit";
}

But it is not working. Is it possible to do this in template.php or I need to build a module to do this? or the problem is from anything else?

Thanks

Answer 1

I think that it solves the problem to do like this

$form['#submit'] = array("my_module_form_submit_handler");

Here's the whole function:

function my_theme_form_alter(&$form, $form_state, $form_id) {
  $form['#submit'] = array("my_module_form_submit_handler");
}

function my_theme_form_submit_handler($form, &$form_state) {
  drupal_set_message("The form is being submitted, do some extra stuff now...");
}