O que ta faltando nesse codigo para fucionar a RSS?

<?php
header("Content-Type: application/xml; charset=iso-8859-1");
header("Expires: Mon, 26 Jul 1997 05:00:00 GMT");
header("Last-Modified: ". gmdate("D, d M Y H:i:s") ." GMT");
header("Cache-Control: no-store, no-cache, must-revalidate");
header("Cache-Control: post-check=0, pre-check=0", false);
header("Pragma: no-cache");
echo '<' . '?xml version="1.0" encoding="ISO-8859-1" ?' . '>';
?>
<rss version="2.0">
<channel>
<title>Gazeta da Paraiba Feed RSS</title>
<link>http://www.gazetadaparaiba.com.br</link>
<description>Gazeta da Paraiba, Seu Portal de Noticias</description>
<language>pt-br</language>
<webMaster>luan_radical@hotmail.com</webMaster>

<?

$conexao = mysql_connect("localhost", "usuario", "senha");
$db = mysql_select_db("meu BD");

$sql = "SELECT * FROM s_noticias ORDER BY data DESC LIMIT 10";

$resultado = mysql_query($sql) or die (mysql_error());

while ($linha=mysql_fetch_array($resultado)) {

 $id = $linha["id"];
 $titulo = $linha["titulo"];

 echo "<item>";
 echo "<title>$titulo</title>";
 echo "<link>http://www.gazetadaparaiba.com.br/?p=noticia&id=$id</link>";
 echo "<description>$titulo ...</description>";
 echo "</item>";
}
?>
</channel>
</rss>