Displaying BBCODES on rss feeds?

[ben07]

How would I be able to display BBcodes on my external feeds?

<?PHP;
 include("header.php");
?>

<?

// ######################################################
// ## configuration
 // ##
 // ## $rss2_file= 'http://www.mysite.com/forum/external.php?type=rss2';
 // ## Adjust this variable to point to your RSS2 feed

 $rss2_file = 'http://www.mysite.com/forum/external.php?type=rss2&forumids=14';

 // ## configuration end
 // ######################################################
 // ## Do not touch code below!

 $is_item = false;
 $tag = '';
 $title = '';
 $description = '';
 $link = '';
 $date = '';
 $poster = '';

 function character_data($parser, $data)
 {
     global $is_item, $tag, $title, $description, $link, $date, $poster;
     if ($is_item)
     {
         switch ($tag)
         {
             case "TITLE":
             $title .= $data;
             break;

             case "DESCRIPTION":
             $description .= $data;
             break;

             case "LINK":
             $link .= $data;
             break;

             case "PUBDATE":
             $date .= $data;
             break;

             case "POSTER":
             $author .= $data;
             break;
         }
     }
 }

 function begin_element($parser, $name)
 {
     global $is_item, $tag;
     if ($is_item)
     {
         $tag = $name;
     }
     else if ($name == "ITEM")
     {
         $is_item = true;
     }
 }

 function end_element($parser, $name)
 {
     global $is_item, $title, $description, $link, $date, $poster, $rss2_output;
     if ($name == "ITEM")
     {
         $rss2_output .= "<dt><strong><a href='" . trim($link) . "'>" . htmlspecialchars(trim($title)) . "</a></strong> <br><i> " . htmlspecialchars(trim($date)) . " </i>Posted by <em>" . htmlspecialchars(trim($poster)) . "</em></dt>" . htmlspecialchars(trim($description)) . "<br><br>";
         $title = "";
         $description = "";
         $link = "";
         $date = "";
         $poster = "";
         $is_item = false;
     }
 }


 $parser = xml_parser_create();

 xml_set_element_handler($parser, "begin_element", "end_element");
 xml_set_character_data_handler($parser, "character_data");
 $fp = fopen($rss2_file,"r");

 while ($data = fread($fp, 4096))
 {
     xml_parse($parser, $data, feof($fp));
 }

 fclose($fp);
 xml_parser_free($parser);
 ?>

 <?
 echo $rss2_output;
 ?>

<?PHP;
 include("below.php");
?>