/**
  * copy_billing_form_data_to_attendee
  * copies info from the billing form to the attendee's details
  * @param \EE_Attendee $attendee - the attendee object to copy details to
  * @return \EE_Attendee
  */
 public function copy_billing_form_data_to_attendee(EE_Attendee $attendee)
 {
     // grab billing form data
     $data = $this->valid_data();
     // copy first_name
     if (!empty($data['first_name'])) {
         $attendee->set_fname($data['first_name']);
     }
     // copy last_name
     if (!empty($data['last_name'])) {
         $attendee->set_lname($data['last_name']);
     }
     // copy email
     if (!empty($data['email'])) {
         $attendee->set_email($data['email']);
     }
     // copy address
     if (!empty($data['address'])) {
         $attendee->set_address($data['address']);
     }
     // copy address2
     if (!empty($data['address2'])) {
         $attendee->set_address2($data['address2']);
     }
     // copy city
     if (!empty($data['city'])) {
         $attendee->set_city($data['city']);
     }
     // copy state
     if (!empty($data['state'])) {
         $attendee->set_state($data['state']);
     }
     // copy country
     if (!empty($data['country'])) {
         $attendee->set_country($data['country']);
     }
     // copy zip
     if (!empty($data['zip'])) {
         $attendee->set_zip($data['zip']);
     }
     // copy phone
     if (!empty($data['phone'])) {
         $attendee->set_phone($data['phone']);
     }
     return $attendee;
 }