drupal_module__url_replace_filter/url_replace_filter.module

<?php
// $Id$

/**
 * Implementation of hook_filter().
 */
function url_replace_filter_filter($op, $delta = 0, $format = -1, $text = '') {
  switch ($op) {
    case 'list':
      return array(0 => t('URL Replace Filter'));

    case 'description':
      return t('Allows administrators to replace the base URL in &lt;img&gt; and &lt;a&gt; elements.');

    case 'settings':
      return _url_replace_filter_settings($format);

    case 'process':
      $text = _url_replace_filter_process($text, $format);
      return $text;

    default:
      return $text;
  }
}

/**
 * Filter the given text.
 */
function _url_replace_filter_process($text, $format) {
  $settings = _url_replace_filter_get_settings($format);
  foreach ($settings as $index => $setting) {
    if ($setting['original']) {
      $pattern = '!((<a\s[^>]*href)|(<img\s[^>]*src))\s*=\s*"'. preg_quote($setting['original']) .'!iU';
      if (preg_match_all($pattern, $text, $matches)) {
        $replacement = str_replace('%baseurl', rtrim(base_path(), '/'), $setting['replacement']);
        foreach ($matches[0] as $key => $match) {
          $text = str_replace($match, $matches[1][$key] .'="'. $replacement, $text);
        }
      }
    }
  }
  return $text;
}

/**
 * Settings for the HTML filter.
 */
function _url_replace_filter_settings($format) {
  $form['#tree'] = TRUE;
  $form['url_replace_filter_'. $format] = array(
    '#type' => 'fieldset',
    '#title' => t('URL Replace Filter'),
    '#collapsible' => TRUE,
    '#collapsed' => FALSE,
    '#theme' => 'url_replace_filter_settings_form',
  );
  $settings = _url_replace_filter_get_settings($format);
  foreach ($settings as $index => $setting) {
    _url_replace_filter_row_form($form, $format, $index, $setting['original'], $setting['replacement']);
    if (!$setting['original']) {
      $empty++;
    }
  }
  // Append some empty fields
  while ($empty < 3) {
    $index++;
    $empty++;
    _url_replace_filter_row_form($form, $format, $index, '', '');
  }
  return $form;
}

function _url_replace_filter_row_form(&$form, $format, $index, $original, $replacement) {
  $form['url_replace_filter_'. $format][$index]['original'] = array(
    '#type' => 'textfield',
    '#size' => 50,
    '#default_value' => $original,
  );
  $form['url_replace_filter_'. $format][$index]['replacement'] = array(
    '#type' => 'textfield',
    '#size' => 50,
    '#default_value' => $replacement,
  );
}

function _url_replace_filter_get_settings($format) {
  return variable_get('url_replace_filter_'. $format, array(0 => array('original' => '', 'replacement' => '')));
}

function theme_url_replace_filter_settings_form(&$form) {
  $header = array(t('Original'), t('Replacement'));
  foreach (element_children($form) as $index) {
    $row = array();
    foreach (element_children($form[$index]) as $key) {
      $row[] = drupal_render($form[$index][$key]);
    }
    $rows[] = $row;
  }
  $output .= '<p>'. t('This filter allows you to replace the base URL in &lt;img&gt; and &lt;a&gt; elements.') .'</p>';
  $output .= theme('table', $header, $rows);
  $output .= t('<p>Enter original base URLs and their replacements. Matching is case-insensitive. You may use %baseurl in the replacement string to insert your site\'s base URL (without the trailing slash).</p><p><strong>Warning</strong>: To avoid unexpected results, you must include trailing slashes in both the original and replacement strings.</p><p><strong>Warning</strong>: Replacements are executed in the order you give them. Place the most specific URLs first. For example, <em>http://example.com/somepath/</em> should be replaced before <em>http://example.com/</em>.</p><p>If you need more replacement rules, more fields will be added after saving the settings.</p>');
  $output .= drupal_render($form);
  return $output;
}