Drupal themeing : Adding active class to the Drupal primary links

This little snippet lives in your phptemplate_variables function and will set a useful 'active' class alongside the not so useful menuid-active class which Drupal assigns to the active primary links

foreach($vars['primary_links'] as $key=>$link){
   if (strpos($key,'-active')){
      $vars['primary_links'][$key]['attributes']['class']='active';
   }
}