private function sanitizeEntry($entry)
    {
        if (!empty($entry)) {
            /* @todo: keys in $entry array that are not yet used and not yet sanitized:
             *   - entrytype
             *   - entrydescription
             *   - entrynote
             *   - fiscaltype
             *   - contactid
             *   - accountnumber
             *   - costcenterid
             *   - costtypeid
             *   - invoicenote
             *   - descriptiontext
             *   - invoicelayoutid
             *   - token
             *   - paymenttermdays
             */
            $result['entryid'] = $this->sanitizeEntryIntValue($entry, 'entryid');
            $result['entrydate'] = $this->sanitizeEntryDateValue($entry, 'entrydate');
            $result['vatreversecharge'] = $this->sanitizeEntryBoolValue($entry, 'vatreversecharge');
            $result['foreigneu'] = $this->sanitizeEntryBoolValue($entry, 'foreigneu');
            $result['foreignnoneu'] = $this->sanitizeEntryBoolValue($entry, 'foreignnoneu');
            $result['marginscheme'] = $this->sanitizeEntryBoolValue($entry, 'marginscheme');
            $result['foreignvat'] = $this->sanitizeEntryBoolValue($entry, 'foreignvat');
            $result['invoicenumber'] = $this->sanitizeEntryIntValue($entry, 'invoicenumber');
            $result['totalvalueexclvat'] = $this->sanitizeEntryFloatValue($entry, 'totalvalueexclvat');
            $result['totalvalue'] = $this->sanitizeEntryFloatValue($entry, 'totalvalue');
            $result['paymentstatus'] = $this->sanitizeEntryIntValue($entry, 'paymentstatus');
            $result['paymentdate'] = $this->sanitizeEntryDateValue($entry, 'paymentdate');
            $result['deleted'] = $this->sanitizeEntryStringValue($entry, 'deleted');
        } else {
            $result = null;
        }
        return $result;
    }