<?php

function multistep_menu($may_cache) {
  if ($may_cache) {
    $items[] = array('path' => 'multistep', 'access' => TRUE, 'title' => 'multistep', 'callback' => 'drupal_get_form', 'callback arguments' => array('multistep_form'));
  }
  return $items;
}

function multistep_form() {
  $form_values = $_POST['edit'];

  $form['#multistep'] = TRUE;

  $current_step = $form_values['step']++;
  $form['step'] = array(
    '#type' => 'hidden',
    '#value' => $current_step,
  );
  switch ($current_step) {
    case 1:
      $form['title'] = array(
        '#type' => 'textfield',
        '#title' => t('Title'),
      );
      break;
    case 2:
      $form['title'] = array(
        '#type' => 'hidden',
        '#value' => $form_values['title'],
      );
      $form['body'] = array(
        '#type' => 'textarea',
        '#title' => t('Body'),
      );
      break;
    case 3:
      $form['title'] = array(
        '#type' => 'hidden',
        '#value' => $form_values['title'],
      );
      $form['body'] = array(
        '#type' => 'hidden',
        '#value' => $form_values['body'],
      );
      $form['notes'] = array(
        '#type' => 'textarea',
        '#title' => t('Other notes'),
        '#default_value' => 'Pre-populated with Hello Kitty info.',
      );
      if ($form_values['title'] == 'Hello Kitty') {
        $form['notes']['#default_value'] = 'Pre-populated with Hello Kitty info.';
      }
      break;
    default:
      $form['huh'] = array(
        '#type' => 'value',
        '#value' => t('goofy')
      );
  }
  return $form;
}