Error with Xajax using PHP and Smarty

Hello, Please help it's urgent.

I am trying to use smarty template with Xajax class, but getting following error: ERROR: No response processor is available to process the response from the server.Content-Type: text/html; charset=UTF-8

Following is the code that I am using. Please help if any one can.
I am using three files
1. default.php
2. reg_functions.php
3. registration.tpl



default.php
***********
require_once ("/home/Data/project/Xajax/xajax_core/xajax.inc.php"); // Include xajax.inc class

$xajax = new xajax("http://192.168.0.43/project/registration/reg_functions.php");
$xajax->configure('debug', true); // Turn degub on so that we can catch the error

//Register Function
$xajax->registerFunction("testFun");

$xajax->printJavascript('http://192.168.0.43/project/Xajax/');

//Showing template
$smarty->display('registration.tpl');
------------------------------

reg_functions.php
*****************
require_once ("/home/Data/project/Xajax/xajax_core/xajax.inc.php");

$xajax = new xajax();
$xajax->registerFunction("testFun");

function testFun() {
$objResponse = new xajaxResponse();

$objResponse->alert("Hello Sandeep");

return $objResponse;
}

$xajax->processRequest();
-------------------------------

registration.tpl (This file is at the location: "/home/Data/project/Smarty/templates/" )
*****************
<a href="#" class="" onclick="xajax_testFun();">Test Now</a>
-------------------------------

Thanks & regards,
Sandeep Limbachiya (phpwebs.org)