PayPal\PayPalAPI\BMUpdateButtonRequestType::toXMLString PHP Метод

    public function toXMLString()
    {
        $flag = 0;
        foreach ($this->ButtonVar as $var) {
            if (strpos($var, 'bn=') !== false) {
                $flag = 1;
                break;
            }
        }
        if (!$flag) {
            array_push($this->ButtonVar, "bn=PayPal_SDK");
        }
        return parent::toXMLString();
    }

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