Ajax dont return values in drupal 7 - ajax

Question

Im in drupal 7, i need to make a select with many options, depends of the option taken, in a textarea will be loaded several values in a string.
After hours of test i come here for help.
Im working on a basic page:
function ajax_load_all_admins($form, &$form_state) {
$form = array();
$form['changethis'] = array(
'#type' => 'select',
'#options' => array(
'' => '',
'1' => 'Cargar todos los admins'
),
'#ajax' => array(
'event' => 'change',
'callback' => 'ajax_load_all_admins_callback',
'wrapper' => 'listaCorreos-div'
)
);
$form['listaCorreos'] = array(
'#type' => 'textarea',
'#prefix' => '<div id="listaCorreos-div">',
'#suffix' => '</div>'
);
if (!empty($form_state['values']['changethis'])) {
$payments_list = db_query('QUERY WORKING WELL');
$value = '';
foreach ($payments_list as $payment) {
$value .= $payment->admin . ',';
}
trim($value, ',');
$form['listaCorreos']['#default_value'] = $value;
}
return $form;
}
function ajax_load_all_admins_callback($form, $form_state) {
return $form['listaCorreos'];
}
$form = drupal_get_form('ajax_load_all_admins');
print drupal_render($form);
The Ajax call is working but i only recibe:
0: {command:settings, settings:{basePath:/, pathPrefix:,…}, merge:true}
No other one position.
I think it can be for the drupal_render, but dont know why?
Thanks in advice.

Answer 1

since the ajax itself works;
Looks to me like the db_query isn't working well and/or returning unexpected results.
My advice: You should be able to debug. i.e. setting a breakpoint and stepping into your code line by line
I do it with netbeans & XDEBUG
This should gives you a great edge solving this & upcoming similar problems, as you'll be able to monitor your variables & the execution tree of your code
Best of luck.
--edit-- This should be totally in the comment section, but ... new here , cant comment at the moment.. apologies.

Answer 2

I was doing this ajax functions in a simple view, created to make an specific form.
I move all the logic to a new module, instead of simple view and now is working.
I take a look to the ajax examples of "examples module" and test if they works on a simple view,like my code, dont works.
I think for any reason, drupal ajax only works if the render is not manually, like i was doing.
Thanks.