Accessing .net web service from php

hello friends,

          i need a help from you.
          i have developed a web service using c#. and i want to access it from a php page. i am giving the code i am using but still not working.

the webservice has a simple sum method which returns a integer value

require_once('nusoap.php');
$proxyhost = 'MYHOST';
$proxyport = '8080';
$proxyusername = 'username';
$proxypassword = 'pass';

$wsdl="http://localhost/testwebservice/service.asmx?wsdl";

try
{
$client=new nusoap_client($wsdl,false);
}
catch(Exception $e)
{
printf("Message = %s\n",$e->getMessage());
}

$params = array(
    'a'                 => 2,
    'b'                => 4,
    );

try
{
$result = $client->call('sum',array('parameters' => $params));

}
catch(EXception $e1)
{
printf("Message = %s\n",$e1->getMessage());
}
if ($client->fault)
{
    echo '
Fault
';
    print_r($result);
    echo '
';
}
else
{
    // Check for errors
    $err = $client->getError();
    if ($err)
    {
        // Display the error
        echo '
Error
' . $err . '
';

    } else
    {
        // Display the result
        echo '
Result
';
        print_r($result);
        echo '
';
    }
}
echo '
Request
' . htmlspecialchars($client->request, ENT_QUOTES) . '
';
echo '
Response
' . htmlspecialchars($client->response, ENT_QUOTES) . '
';
echo '
Debug
' . htmlspecialchars($client->getDebug(), ENT_QUOTES) . '
';

?>

please help me guyz