How can I dynamically load options into a select list?

Question

I'm creating form using drupal_get_form and I'm using the following code for creating a select list:

$form['select-user-group'] = array(
  '#type' => 'select',
  '#title' => t('Select a group'),
  '#options' => array(
    '' => t('-- Select a user group --'),        
  ),
  '#ajax' => array(
  'event' => 'load',
  'callback' => 'selectuser_ajax_callback',
  'method' => 'replace',
);

and then I'm trying to define a function like following to dynamically add options to the select list:

function selectuser_ajax_callback() {

  db_set_active('drupal');

  $result = db_query("select * from {content_type_usergroup}");
  $record = db_fetch_object($result);

  $str = '<select>';
  while ($obj = db_fetch_object($result)) {
    $str .= '<option value=' + $obj->vid + '>' + $obj->field_p_group_name_value + '</option>';
  }
  $str .= '</select>';

  echo $str;
}

But it's not working. How to make this function work properly to populate the select list '#options?

Answer 1

For just populating select list options, you don't need to go through an Ajax approach! Simply write a separate function and write your database query inside it and then just call that function in '#options' of your $form['select-user-group'].

For example for displaying all node types in a select list you can use the following function:

function get_node_type_info() {

  $wizard_plugins = node_type_get_types();

  $options = array();

  foreach ($wizard_plugins as $key => $wizard) {
    // Don't forget the $ before wizard
    $options[$key] = $wizard->name;
  }

  return $options;
}

And then use this function to populate the '#options' like so:

$form['display_options'] = array(
  '#type' => 'select',
  '#title' => t('Component Type'),
  '#options' => get_node_type_info(),
);