How to create Drupal pagination that use rel=“next” and rel=“prev”

If you want to optimize your Drupal site pages to have HTML link elements rel=”next” and rel=”prev” to indicate the relationship between component URLs in a paginated series here is what you need to do (note that this example is written for Drupal 6, but Drupal 7 solution should be similar).

Drupal pager rendering is controlled by couple of theme functions theme_pager, theme_pager_first, theme_pager_last, theme_pager_previous, theme_pager_next, theme_pager_link. Of all this theme function best is to override theme_pager_link which you will add into your template.php theme file. You just to change end of theme_pager_link function and add next lines of code:

<?php
  $query = count($query) ? implode('&', $query) : NULL;

  // Pagination with rel=“next” and rel=“prev”. Does not support well multiple
  // pagers on the same page - it will create relnext and relprev links
  // in header for that case only for the first pager that is rendered.
  static $rel_prev = FALSE, $rel_next = FALSE;
  if (!$rel_prev && $text == t('‹ previous')) {
    $rel_prev = TRUE;
    drupal_set_html_head('<link rel="prev" href="' . url($url, array('query' => $query)) . '" />');
  }
  if (!$rel_next && $text == t('next ›')) {
    $rel_next = TRUE;
    drupal_set_html_head('<link rel="next" href="' . url($url, array('query' => $query)) . '" />');
  }
  
  return l($text, $url, array('attributes' => $attributes, 'query' => $query));
?>

So your whole function should look like this:

<?php
function theme_pager_link($text, $page_new, $element, $parameters = array(), $attributes = array()) {
  $page = isset($_GET['page']) ? $_GET['page'] : '';
  if ($new_page = implode(',', pager_load_array($page_new[$element], $element, explode(',', $page)))) {
    $parameters['page'] = $new_page;
  }

  $query = array();
  if (count($parameters)) {
    $query[] = drupal_query_string_encode($parameters, array());
  }
  $querystring = pager_get_querystring();
  if ($querystring != '') {
    $query[] = $querystring;
  }

  // Set each pager link title
  if (!isset($attributes['title'])) {
    static $titles = NULL;
    if (!isset($titles)) {
      $titles = array(
        t('« first') => t('Go to first page'), 
        t('‹ previous') => t('Go to previous page'), 
        t('next ›') => t('Go to next page'), 
        t('last »') => t('Go to last page'),
      );
    }
    if (isset($titles[$text])) {
      $attributes['title'] = $titles[$text];
    }
    else if (is_numeric($text)) {
      $attributes['title'] = t('Go to page @number', array('@number' => $text));
    }
  }

  $query = count($query) ? implode('&', $query) : NULL;
  
  // Pagination with rel=“next” and rel=“prev”. Does not support well multiple
  // pagers on the same page - it will create relnext and relprev links
  // in header for that case only for the first pager that is rendered.
  static $rel_prev = FALSE, $rel_next = FALSE;
  if (!$rel_prev && $text == t('‹ previous')) {
    $rel_prev = TRUE;
    drupal_set_html_head('<link rel="prev" href="' . url($url, array('query' => $query)) . '" />');
  }
  if (!$rel_next && $text == t('next ›')) {
    $rel_next = TRUE;
    drupal_set_html_head('<link rel="next" href="' . url($url, array('query' => $query)) . '" />');
  }
  
  return l($text, $url, array('attributes' => $attributes, 'query' => $query));
}
?>

Note that this solution will work well when you have only one pager on your page, but it will not work well in situation if you have multiple pagers on your page this code will create rel prev/next head links only for first rendered pager.