public function toXMLString() { $str = ''; $str .= '<ns:BillAgreementUpdateReq>'; if ($this->BAUpdateRequest != null) { $str .= '<ns:BAUpdateRequest>'; $str .= $this->BAUpdateRequest->toXMLString(); $str .= '</ns:BAUpdateRequest>'; } $str .= '</ns:BillAgreementUpdateReq>'; return $str; }