Microdata with Bootstrap 3 theme

Just to save others some troubleshooting time, here's how to deal with quirks of the Bootstrap 3 theme. Both path_breadcrumbs and Bootstrap implement hook_theme_registry_alter, and the theme implementation wins the contest. This means the path_breadcrumbs "Use module breadcrumbs render function" has no effect and the nice Microdata feature can't be used. The workaround is to copy the path_breadcrumbs_breadcrumb theme_breadcrumb() implementation from path_breadcrumbs.module into the Bootstrap sub-theme's template.php file. After renaming the function, it also needs slight modification to use an ol and li structure, and removal of the delimeters in order to work well with the Bootstrap CSS. It's not enough to delete the delimiter in the path_breacrumbs settings since the span still get printed and interferes. Rename and paste the following into the subtheme's template.php.

function [subtheme-name]_breadcrumb($variables) {
  $breadcrumbs = $variables['breadcrumb'];
  if (!empty($breadcrumbs)) {
    // Provide a navigational heading to give context for breadcrumb links to
    // screen-reader users. Make the heading invisible with .element-invisible.
    $output = '<h2 class="element-invisible">' . t('You are here') . '</h2>';

    // Hide breadcrumb navigation if it contains only one element.
    $hide_single_breadcrumb = variable_get('path_breadcrumbs_hide_single_breadcrumb', 0);
    if ($hide_single_breadcrumb && count($breadcrumbs) == 1) {
      return FALSE;
    }

    // Bootstrap 3 compatibility. See: https://drupal.org/node/2178565
    if (is_array($breadcrumbs[count($breadcrumbs) - 1])) {
      array_pop($breadcrumbs);
    }

    // Add options for rich snippets.
    $elem_tag = 'span';
    $elem_property = '';
    $root_property = '';
    $options = array('html' => TRUE);
    $snippet = variable_get('path_breadcrumbs_rich_snippets', PATH_BREADCRUMBS_RICH_SNIPPETS_DISABLED);
    if ($snippet == PATH_BREADCRUMBS_RICH_SNIPPETS_RDFA) {

      // Add link options for RDFa support.
      $options['attributes'] = array('rel' => 'v:url', 'property' => 'v:title');
      $options['absolute'] = TRUE;

      // Set correct properties for RDFa support.
      $elem_property = ' typeof="v:Breadcrumb"';
      $root_property = ' xmlns:v="http://rdf.data-vocabulary.org/#"';
    }
    elseif ($snippet == PATH_BREADCRUMBS_RICH_SNIPPETS_MICRODATA) {

      // Add link options for microdata support.
      $options['attributes'] = array('itemprop' => 'url');
      $options['absolute'] = TRUE;

      // Set correct properties for microdata support.
      $elem_property = ' itemscope itemtype="http://data-vocabulary.org/Breadcrumb"';
      $elem_tag = 'li';

    }

    foreach ($breadcrumbs as $key => $breadcrumb) {

      // Build classes for the breadcrumbs.
      $classes = array('inline');
      $classes[] = $key % 2 ? 'even' : 'odd';
      if ($key == 0) {
        $classes[] = 'first';
      }
      if (count($breadcrumbs) == $key + 1) {
        $classes[] = 'last';
      }

      // For rich snippets support all links should be processed in the same way,
      // even if they are provided not by Path Breadcrumbs module. So I have to
      // parse html code and create links again with new properties.
      preg_match('/href="([^"]+?)"/', $breadcrumb, $matches);

      // Remove base path from href.
      $href = '';
      if (!empty($matches[1])) {
        global $base_path;
        global $language;

        $base_string = rtrim($base_path, "/");

        // Append additional params to base string if clean urls are disabled.
        if (!variable_get('clean_url', 0)) {
          $base_string .= '?q=';
        }

        // Append additional params to base string for multilingual sites.
        // @note: Only core URL detection method supported.
        $enabled_negotiation_types = variable_get("language_negotiation_language", array());
        if (!empty($enabled_negotiation_types['locale-url']) && !empty($language->prefix)) {
          $base_string .= '/' . $language->prefix;
        }

        // Means that this is href to the frontpage.
        if ($matches[1] == $base_string || $matches[1] == '' || $matches[1] == '/') {
          $href = '';
        }
        // All hrefs exept frontpage.
        elseif (stripos($matches[1], "$base_string/") === 0) {
          $href = drupal_substr($matches[1], drupal_strlen("$base_string/"));
        }
        // Other cases.
        else {
          // HREF param can't starts with '/'.
          $href = stripos($matches[1], '/') === 0 ? drupal_substr($matches[1], 1) : $matches[1];
        }

        // If HREF param is empty it should be linked to a front page.
        $href = empty($href) ? '<front>' : $href;
      }

      // Get breadcrumb title from a link like "<a href = "/path">title</a>".
      $title = trim(strip_tags($breadcrumb));

      // Wrap title in additional element for microdata support.
      if ($snippet == PATH_BREADCRUMBS_RICH_SNIPPETS_MICRODATA) {
        $title = '<span itemprop="title">' . $title . '</span>';
      }

      // Support title attribute.
      if (preg_match('/<a\s.*?title="([^"]+)"[^>]*>/i', $breadcrumb, $attr_matches)) {
        $options['attributes']['title'] = $attr_matches[1];
      }
      else {
        unset($options['attributes']['title']);
      }

      // Decode url to prevent double encoding in l().
      $href = rawurldecode($href);
      // Move query params from $href to $options.
      $href = _path_breadcrumbs_clean_url($href, $options, 'none');

      // Build new text or link breadcrumb.
      $new_breadcrumb = !empty($href) ? l($title, $href, $options) : $title;

      // Replace old breadcrumb link with a new one.
      $breadcrumbs[$key] = '<' . $elem_tag . ' class="' . implode(' ', $classes) . '"' . $elem_property . '>' . $new_breadcrumb . '</' . $elem_tag . '>';
    }

    $classes = array('breadcrumb');

    // Show contextual link if it is Path Breadcrumbs variant.
    $prefix = '';
    $path_breadcrumbs_data = path_breadcrumbs_load_variant(current_path());
    if (user_access('administer path breadcrumbs') && $path_breadcrumbs_data && isset($path_breadcrumbs_data->variant)) {
      $contextual_links = array(
        '#type' => 'contextual_links',
        '#contextual_links' => array('path_breadcrumbs' => array('admin/structure/path-breadcrumbs/edit', array($path_breadcrumbs_data->variant->machine_name))),
      );
      $prefix = drupal_render($contextual_links);
      $classes[] = 'contextual-links-region';
    }

    // Build final version of breadcrumb's HTML output.
    $output .= '<ol class="' . implode(' ', $classes) . '"' . $root_property . '>' . $prefix . implode(" ", $breadcrumbs) . '</ol>';

    return $output;

  }
  // Return false if no breadcrumbs.
  return FALSE;
}