在这个方法中写如下代码，watchdog里面提示Invalid form POST data.
function options_form(&$form, &$form_state) {
$form['entity_settings']['entity_select'] = array(
// '#title' => t('node type'),
// '#options' => node_type_get_names(),
// '#type' => 'select',
// '#description' => t('Choose a node type'),
// '#default_value' => isset($this->options['entity_settings']['entity_select']) ? $this->options['entity_settings']['entity_select'] : array(),
// '#dependency' => array( 'edit-options-element-type-enable' => array(1), ),
// '#ajax' => array(
// 'callback' => 'entity_select_callback',
// 'wrapper' => 'entity-select-wrapper-div',
// 'method' => 'replace',
// 'effect' => 'fade',
// )
// );