AJAX callback function never called

Question

I'm having trouble with something incredibly simple: When I select an element in a multiselect-form element, I want a textfield to become enabled. The problem I'm having is that Drupal never manages to get in the callback-function I specified.

Here I create my multiselect-element:

$form['foocat'] = array(
  '#type' => 'fieldset', 
  '#title' => t('Manage subcategories'), 
  '#prefix' => '<div class="fieldset">',
  '#suffix' => '</div>',
);
$form['foocat']['subcategories'] = array(
  '#type' => 'select',
  '#default_value' => '',
  '#title' => $foocategory,
  '#options' => $options,
  '#ajax' => array(
    'callback' => 'edit_displayname_callback', 
    'wrapper' => 'displayname',
  ),
  '#attributes' => array('id' => 'foocats',),
  '#prefix' => '<div class="formselect" id="selectmapcat">',
  '#suffix' => '</div>',
  '#size' => 9,
);

A little bit further in the code I create my textfield:

$form['foocat']['subcat_displayname'] = array(
  '#type' => 'textfield',
  '#title' => t('Name'),
  '#default_value' => $entity->foocategory,
  '#size' => 25,
  '#maxlength' => 31,
  '#prefix' => '<div class="floater" id="displayname">',
  '#suffix' => '</div>',
  '#disabled' => TRUE,
);

if(!empty($form_state['subcategories'])) {
  $form['foocat']['subcat_displayname']['#disabled'] = FALSE; 
  //Code for setting the textfield, dependent on what's been selected in the multiselect
}

And this is my callback function:

function edit_displayname_callback($form, &$form_state) {
  watchdog("Test", "Testing callback..", array(), WATCHDOG_ALERT);
  return $form['foocat']['subcat_displayname'];
}

The callback is never even called, and I have no idea why. I use AJAX in another part of the same form, and there it does work, so I'm guessing it's not a form problem.

Can anyone spot the problem?

Answer 1

I guess you are changing the id with '#attributes' => array('id' => 'foocats',), And now the callback is not executed because the id is changed.

if you change your code it will work ( tested this in my own install )

$form['foocat']['subcategories'] = array(
  '#type' => 'select',
  '#default_value' => '',
  '#title' => $foocategory,
  '#options' => $options,
  '#ajax' => array(
    'callback' => 'edit_displayname_callback', 
    'wrapper' => 'displayname',
  ),
  //'#attributes' => array('id' => 'foocats',),
  '#prefix' => '<div class="formselect MY_SPECIAL_JQUERY_SELECTOR" id="selectmapcat">',
  '#suffix' => '</div>',
  '#size' => 9,
);