private function sendReturnReceipt()
 {
     $mail = new Mailing();
     $mail->setMailTo($this->email);
     $mail->setSubject(PAYPALRECEIPTSUBJECT);
     $body = PAYPALRECEIPTBODY;
     $body = str_replace("<time>", $this->transactionTime, $body);
     $body = str_replace("<id>", $this->transactionID, $body);
     $body = str_replace("<amount>", $this->amount, $body);
     $mail->setBody($body);
     $mail->send();
 }