IBAN\Rule\DE\Rule004201::generateIban PHP Method

    public function generateIban()
    {
        $floatbankAccountNumber = floatval($this->bankAccountNumber);
        if (strlen($this->bankAccountNumber) == 8) {
            // nnn 0 0000 to nnn 0 0999 are not converted
            $lastFive = floatval(substr($this->bankAccountNumber, -5));
            if ($lastFive >= 0 && $lastFive <= 999) {
                return "";
            }
            if (substr($this->bankAccountNumber, 3, 1) == 0 || $floatbankAccountNumber >= 50462000 && $floatbankAccountNumber <= 50463999 || $floatbankAccountNumber >= 50469000 && $floatbankAccountNumber <= 50469999) {
                return parent::generateIban();
            }
        }
        if (strlen($this->bankAccountNumber) == 10) {
            // only nnn 44 00001 to nnn 44 99999 can be converted
            $lastSeven = floatval(substr($this->bankAccountNumber, -7));
            if ($lastSeven >= 4400001 && $lastSeven <= 4499999) {
                return parent::generateIban();
            }
        }
        return "";
    }