public function toXMLString()
 {
     $str = '';
     $str .= '<ns:CreateBillingAgreementReq>';
     if ($this->CreateBillingAgreementRequest != NULL) {
         $str .= '<ns:CreateBillingAgreementRequest>';
         $str .= $this->CreateBillingAgreementRequest->toXMLString();
         $str .= '</ns:CreateBillingAgreementRequest>';
     }
     $str .= '</ns:CreateBillingAgreementReq>';
     return $str;
 }
 public function toXMLString()
 {
     $str = '';
     $str .= '<urn:CreateBillingAgreementReq>';
     if ($this->CreateBillingAgreementRequest != null) {
         //prop is not a collection
         //prop is complex
         //prop is not enum
         //does not contain attribute or is attribute
         $str .= '<urn:CreateBillingAgreementRequest>';
         $str .= $this->CreateBillingAgreementRequest->toXMLString();
         $str .= '</urn:CreateBillingAgreementRequest>';
     }
     $str .= '</urn:CreateBillingAgreementReq>';
     return $str;
 }