function twitify($str)
{
    $str = preg_replace("#(^|[\n ])([\w]+?://[\w]+[^ \"\n\r\t< ]*)#", "\\1<a href=\"\\2\" target=\"_blank\">\\2</a>", $str);
    $str = preg_replace("#(^|[\n ])((www|ftp)\.[^ \"\t\n\r< ]*)#", "\\1<a href=\"http://\\2\" target=\"_blank\">\\2</a>", $str);
    $str = preg_replace("/@(\w+)/", "@<a href=\"http://www.twitter.com/\\1\" target=\"_blank\">\\1</a>", $str);
    $str = preg_replace("/#(\w+)/", "#<a href=\"http://search.twitter.com/search?q=\\1\" target=\"_blank\">\\1</a>", $str);
    return $str;
}