When using hook_form_alter() and additional submit functions, can one reference a php file for the submit callback? The following code works.

function bleh_form_alter(&amp;$form, &amp;$form_state, $form_id) {

  switch ($form_id) {
    case "webform_client_form_13":
      $form['#submit'][] = 'bleh_community_submit';
      break;
  }
}

function bleh_community_submit($form, &amp;$form_state) {
  // Do some stuff here.
}


However, is it possible to use code similar to the following one, where the form submit function calls a PHP script (e.g. bleh_community_submit.php) containing the form submission handler?

function bleh_form_alter(&amp;$form, &amp;$form_state, $form_id) {
  switch ($form_id) {
    case "webform_client_form_13":
      $form['#submit'][] = 'bleh_community_submit.php';
      break;
  }
}

// Separate .php file in the module directory with the 
   additional bleh_community_submit function

function bleh_community_submit($form, &amp;$form_state) {
  // Do some stuff here.
}
Why not do something like 

require_once('bleh_community_submit.php');


then call the callback function as per normal?