private function _buildSAMLPayload()
{
phpCAS::traceBegin();
//get the ticket
$sa = urlencode($this->getTicket());
$body = SAML_SOAP_ENV . SAML_SOAP_BODY . SAMLP_REQUEST . SAML_ASSERTION_ARTIFACT . $sa . SAML_ASSERTION_ARTIFACT_CLOSE . SAMLP_REQUEST_CLOSE . SAML_SOAP_BODY_CLOSE . SAML_SOAP_ENV_CLOSE;
phpCAS::traceEnd($body);
return $body;
}