Problem with xml-rpc

[girishso]

I am using Apache 2.0.46 with PHP 4.3.2
I am trying to run a simple xml-rpc server

 
<?
include("xmlrpc.inc");
include("xmlrpcs.inc");

function onttax($par)
{
 $amount=$par->getParam(0); 
 $amountval=$amount->scalarval();
 $taxcalc=$amountval*.15;
 return new xmlrpcresp(new      xmlrpcval($taxcalc, "string"));
}
$server=new xmlrpc_server(array("taxcalc.onttax" => array("function" => "onttax")));
?>

However I get following error if I try to open http://localhost/testrpc.php?amount=10 in browser

<methodResponse>

<fault>

<value>

<struct>

<member>

<name>faultCode</name>

<value>
<int>103</int>
</value>

</member>

<member>

<name>faultString</name>

<value>
<string>XML error: no element found at line 1</string>
</value>
</member>
</struct>
</value>
</fault>
</methodResponse>

What am I doing wrong??

Thanks,
Girish