Drupal 7 AJAX does not replace content, instead inserts empty div

With respect, gwalliman hasn't asked to add form elements, if they had I would not have shown the solution I did, that is a completely different functionality. Also, this is not akin to core hacking, or the other things you mention.

If gwalliman shouldn't do it the way I offered, could you show an example of how it should be done? Perhaps your example will change my mind, and I'm really interested to see the way you'd do it. I think if you are saying something is wrong, you need to offer up the right way of doing it. :)

Have you got FirePHPCore installed? If so you can do the below test, if not follow instructions here to install first:

<?php
function yourmodule_form_alter(&$form, &$form_state, $form_id) {
    
  // show $form_state['values] in FirePHPCore
  $path = libraries_get_path('FirePHPCore');
  if (file_exists($path . '/fb.php')) {
    include_once $path . '/fb.php';
    include_once $path . '/FirePHP.class.php';
  }
  isset($form_state['values']) ? dfb($form_state['values'], 'ERROR', FirePHP::ERROR) : '';

  if ($form_id == 'test_node_form') {
    $form['field_test_textfield'] = array(
      '#type' => 'textfield',
      '#default_value' => '',
      '#weight' => -10,
      '#ajax' => array(
        'callback' => 'ajax_example_submit_driven_callbacktest',
        'wrapper' => 'test_ajax_field',
        'name' => 'submit1',
      ),
      '#prefix' => '<div id="test_ajax_field">',
    );
    $form['field_test_submit'] = array(
      '#type' => 'button',
      '#ajax' => array(
        'callback' => 'ajax_example_submit_driven_callbacktest',
        'wrapper' => 'test_ajax_field',
        'name' => 'submit1',
      ),
      '#value' => t('Update'),
      '#weight' => -10,
      '#limit_validation_errors' => array(),
      '#suffix' => '</div>',
    );
  }
}

function ajax_example_submit_driven_callbacktest($form, $form_state) {
  return $form;
}
?>

The above code is showing, using AJAX, button vs textfield and how they differ in $form_state['values'] output. This is the reason why, for buttons, I'd say put the logic in the callback as the values aren't available like they would be for the textfield.

You will not see $form_state['values'] filled in unless you are looking at the form generation when it's being created through #ajax. The reason for this is that in the initial form definition, the form hasn't yet been submitted, so there are no values to be filled in. However when the form is rebuilt during an ajax call, $form_state['values'] will exist. I believe the values in $form_state['input'] are unsanitized, so using them is a security risk.

#AJAX testing when creating a form definition can be quite difficult without a debugger installed - but I don't use a debugger myself. To do AJAX testing, I do the following:

1) I use firefox with the firebug plugin, set to the console tab.
2) I load the form normally through an HTTP request
3) I edit the code, and add my debugging code into the form definition. For example, at the top of the form definition I often do this:

function my_form($form, &$form_state)
{
  die(print_r($form_state['values']));
}

4) I then trigger my #ajax call (note, this will cause an error, but that's ok, it's expected)
5) The AJAX call is shown in the console tab of firebug. This can be expanded to see the response. Since the form generation has been killed with a dump of the $form_state['values'] element, this is listed as the response of the call

In this way, I can see what is in $form_state['values'] in an #AJAX call, and change my form definition accordingly.

I also can't help but notice jay is still here in the forums helping people out day after day

You have to wonder why people would take any advice I give, considering that according to Web Assistant I don't know what I'm doing :)