HTML Link element with rel="alternate" for multilingual Drupal website

gistfile1.aw

<?php
/**
 * More info : http://www.google.com/support/webmasters/bin/answer.py?answer=189077&hl=en
 */

/**
 * Implements hook_preprocess_page()
 */
function mymodule_preprocess_page(&$vars) {
  global $language;
  
  // Get enabled languages, and remove current
  $languages = array_pop(language_list('enabled'));
  unset($languages[$language->language]);

  // Get path
  $path = drupal_is_front_page() ? '<front>' : $_GET['q'];
  
  // Get urls
  $links = array();
  foreach($languages as $lang) {
    $links[$lang->language] = array(
      'href' => $path,
      'language' => $lang,
      'absolute' => TRUE,
    );
  }
  drupal_alter('translation_link', $links, $path);
  
  // Set head tags
  foreach($links as $link) {
    drupal_set_html_head('<link rel="alternate" hreflang="'. $link['language']->language .'" href="'. url($link['href'], $link) .'" />');
  }
  
  // Update head
  $vars['head'] = drupal_get_html_head();
}

Last google info : http://googlewebmastercentral.blogspot.com/2011/12/new-markup-for-multilingual-content.html

In my case I had to use array_shift() instead of array_pop() at the line where language_list('enabled') is called, otherwise I get the disabled languages ;-)

On a second thought, a better solution is to replace this line with the following two:

$languages = language_list('enabled');
$languages = $languages[1];

This will solve the issue no matter where the position of the enabled languages is in the array.