Burn a feed right this instant as podcaster

[netonplus.com netonplus]

Dear Friend can anyone please help me?

I was trying to use feedburner.google.com as podcaster for my website www.netonplus.com

For that , I have created a folder called feed under http://netonplus.com/ that is http://netonplus.com/feed 

and created an xml file called  feedbur.php.xml  and Coding for feedburner.php.xml page is as below 

=====Start ======

<?php 

ob_start();

include("db.php");

ob_end_clean();

?>

<?xml version="1.0"?>

<rss version="2.0" 

xmlns:g="http://base.google.com/ns/1.0">

<channel>

<title>NetonPlus</title>

<link>http://netonplus.com</link>

<description>NetOnPlus is a leading science and technology media property, devoted to enthusiastically outlining entrepreneurs, analyzing new Internet products, and breaking tech news.</description>

<?php $url=$_REQUEST['url'];?>

<?php  $qry = mysql_query("SELECT * FROM articles WHERE url='$url'", $con);

while($row = mysql_fetch_array($qry))

 {

 ?> 

<item>

<title><?php echo $row['title']; ?></title>

<link> http://www.netonplus.com/<?php echo $row['url']; ?></link>

<description><?php echo $row['summary']; ?></description>

<g:image_link>http://netonplus.com/admin/imgupload/<?php echo $row['image'] ?>"  alt="<?php echo $row['title']; ?></g:image_link>

</item>

<?php   } 

 ?>  

</channel>

</rss>

=====End =====

After that I kept the file feedbur.php.xml under feed folder that is http://netonplus.com/feed/feedbur.php.xml . Then I am using this url (http://netonplus.com/feed/feedbur.php.xml) for podcaste at feedburner.. but its giving error like  "Received HTTP error: "Internal Server Error" while fetching source feed."

Please tell me what mistake I have done ?

Thanks