dofollow / nofollow

Old post but get the same issue, so i made a tiny module for Drupal 6 to add dofollow filter formats option.

<?php

/**
 * @file
 * This module add filter option to set dofollow to links.
 */

/**
 * Implementation of hook_filter_tips().
 */
function dofollow_filter_tips($delta, $format, $long = FALSE) {
  switch ($delta) {
  case 0:
    return t('Each link will be added dofollow attribute.');
    break;
  }
}
 
/**
 * Implementation of hook_filter().
 */
function dofollow_filter($op, $delta = 0, $format = -1, $text = '', $cache_id = 0) {
  switch ($op) {
    case 'list':
      return array(0 => t('Add dofollow attribute on links'));

    case 'description':
      return t('Add dofollow attributes on each links.');

    case 'no cache':
      return FALSE;

    case 'prepare':
      return $text;

    case 'process':
      $text = preg_replace('/<a([^>]+)>/i', '<a\\1 rel="dofollow">', $text);
      return $text;

    default:
      return $text;
  }
}