gistfile1.aw

<?php
/**
 * @file
 * Custom functions for the congr site.
 */

/**
 * Implements hook_form_alter().
 */
function congr_form_alter(&$form, $form_state, $form_id) {
  // Add an additional validation handler.
  if ($form_id == 'uc_cart_view_form') {
    $form['#validate'][] = 'congr_afternoon_bookings_validate';
  }
}

/**
 * Additional validation handler for uc_cart_view_form.
 *
 * Checks afternoon tours for a maximum of 2 bookings.
 *
 * @see congr_form_alter()
 */
function congr_afternoon_bookings_validate(&$form, &$form_state) {
  $congr_highlight_afternoon_fields = array();
  $congr_max_afternoon = 0;

  if (!empty($form['items'])) {
    foreach ($form['items'] as $key => &$value) {
      if (isset($value['nid']['#value'])) {
        // Load the node of the corresponding item in the form.
        $node = node_load($value['nid']['#value']);

        // If the associated term tid is 476, add the quantity field of the
        // item list to our maximum value.
        if ($node->field_product_type['und'][0]['tid'] == 476) {
          $congr_max_afternoon += $value['qty']['#default_value'];
          // Collect a list of keys.
          $congr_highlight_afternoon_fields[] = $key;
        }
      }
    }
  }

  // If the maximum number of quantity items is more than 2.
  if ($congr_max_afternoon > 2) {
    $form_state['rebuild'] = TRUE;

    foreach ($congr_highlight_afternoon_fields as $key => $value) {
      $message = t('Please amend this item: %title.', array('%title' => $form['items'][$value]['title']['#markup']);
      // If it is the first one, show the full message which is independent of
      // a specific quantity field
      if ($key == 0) {
        form_set_error('', t('You have tried to buy %number items but the maximum you can buy is 2. See below for a list of items which you can possibly amend.', array('%number' => $congr_max_afternoon));
        form_set_error('items]['. $value, $message);
      }
      // Do not show the message for the rest, only highlight the field.
      else {
        form_set_error('items][' . $value, $message);
      }
    }
  }
}