PayPal\PayPalAPI\BillOutstandingAmountReq::toXMLString PHP Метод

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