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