rss feed not displaying - php

Question

I'm trying to create a rss feed that displays all my news.
So far the code seems to be half way there because if I view page source all the content is there but nothing is showing up on the actual page.
Here is my code rss.php
<?php
ini_set('display_errors', 1);
header("Content-type: text/xml");
include("config.php");
global $NEWS;
$str = '<?xml version="1.0" encoding="utf-8"?>';
$str.= '<rss version="2.0">';
$str.='<channel>';
$sql = "SELECT * FROM $NEWS";
$result = mysql_query($sql) or die ($sql."".mysql_error());
while($row = mysql_fetch_object($result)){
$str.= '<item>';
$str.=' <a href="'.getSEOLink(13).'&article='.$row->id.'">';
$str.= '<title>'.$row->title.'</title></a>';
$str.= '<description><![CDATA['.$row->content. ']]></description>';
$str.= '</item>';
}
$str .='</channel>';
$str .='</rss>';
echo $str;
?>

Answer 1

Why not make use of asXML of SimpleXMLElement ?
<?php
ini_set('display_errors', 1);
include("config.php");
global $NEWS;
$str='<channel>';
$sql = "SELECT * FROM $NEWS";
$result = mysql_query($sql) or die ($sql."".mysql_error());
while($row = mysql_fetch_object($result)){
$str.= '<item>';
$str.=' <a href="'.getSEOLink(13).'&article='.$row->id.'">';
$str.= '<title>'.$row->title.'</title></a>';
$str.= '<description><![CDATA['.$row->content. ']]></description>';
$str.= '</item>';
}
$str .='</channel>';
$xml=new SimpleXMLElement($str);
echo $xml->asXML();

Answer 2

You are apparently generating valid XML (thus your browser is not complaining) but not valid RSS (thus feed readers won't be able to read your stuff). For instance, <a> is not a valid RSS tag and definitively not a child of <item>.
Copy the generated XML (not the PHP source code) and validate it with your favourite RSS validator (e.g. W3C Feed Validation Service).