Debug info for Drupal forms

devel_forms.info

name = Devel forms
description = Tools for developing and debugging Form API.
package = Development
core = 7.x
dependencies[] = devel

devel_forms.module

<?php

/*
 * Implements hook_form_alter().
 */
function devel_forms_form_alter(&$form, &$form_state) {
  $children = devel_forms_children($form);
  foreach ($children as $key => &$child) {
    $child['#attributes']['title'] = $key . ' => ' . print_r($child, TRUE);
  }
}

function devel_forms_children(&$element) {
  $results = array();
  foreach (element_children($element) as $key) {
    $child = &$element[$key];
    if (is_array($child)) {
      if (!empty($child['#type'])) { // OPTIONAL!
        $results[$key] = &$child;
      }
      $results = array_merge($results, devel_forms_children($child));
    }
  }
  return $results;
}