Someone

<?phpfunction linkicons_filter($op, $delta = 0, $format = -1, $text = '') {   switch ($op) {    case 'list':       return array(0 => t('Link Icons filter'));     case 'description':       return t('Bla bla');     case "process":      return preg_replace_callback('!<(a[^>]+)>!i', 'linkicons_callback', $text);     default:       return $text;   }}function linkicons_callback($matches) {  if (preg_match('/href=([\'"][^\'"]+[\'"]|[^ ]+)[ >]/i', $matches[0], $href) && strstr($href[1], '.')) {    list($extension) = array_reverse(explode('.', $href[1]));    $extension = strtolower(preg_replace('![^A-Za-z0-9]!', '', $extension));        if ($extension != '') {      if (preg_match('/class=/i', $matches[0])) {        return preg_replace('!class=["\']?!', '\0url-'. $extension .' ', $matches[0]);      }      else {        return '<'. $matches[1] . ' class="url-'. $extension .'">';      }    }  }  return $matches[0];}$text = <<<DOC<a>test</a><a href="test">test</a><a href="test.xml">test.xml</a><a href="foo.test.xml">test.foo.xml</a><a href="test.ppt" class="foo bar">test.ppt class</a><a href=test.pph class="foooo bar">fooo bar</a>DOC;print nl2br(linkicons_filter('process', 0, -1, $text));?>