/**
 * Implementation of hook_form_alter().
 */
function bigideas_form_alter($form_id, &$form) {
  //dpr($form);
  switch ($form_id) {
    case 'user_register':
      $form['preview'] = array('#type' => 'button', '#value' => t('Continue registration'), '#weight' => 30);
      $form['#after_build'] = array('bigideas_user_register_form_add_preview');
      break;
  }
}

function bigideas_user_register_form_add_preview($form) {
  global $form_values;

  $op = isset($_POST['op']) ? $_POST['op'] : '';
  if ($op == t('Continue registration')) {
    drupal_validate_form($form['form_id']['#value'], $form);
    if (!form_get_errors()) {
      // We pass the global $form_values here to preserve changes made during form validation
      //$form['user_preview'] = array('#value' => dpr($form_values), '#weight' => -100);
      //dpr(element_children($form));
      foreach (element_children($form) as $key) {
        if ($form[$key]['#type'] == 'textfield') {
          $form[$key]['#type'] = 'value';
          
          $form['markup'][$key] = array(
            '#type' => 'markup',
            '#value' => '<strong>'. $form[$key]['#title'] .'</strong>: '. $form_values[$key],
          );
        }
      }
    }
  }
  if (form_get_errors() || $op != t('Continue registration')) {
    unset($form['submit']);
  }
  //dpr($form);
  return $form;
}