protected function checkForDev(): bool
    {
        $return = false;

        if (\function_exists('checkForDev')) {
            $return = checkForDev();
        } else {

            // for testing with dev-address
            $noDev = isset($_GET['noDev']) ? (int) $_GET['noDev'] : 0;
            $remoteAddr = $_SERVER['REMOTE_ADDR'] ?? 'NO_REMOTE_ADDR';

            if (
                $noDev !== 1
                &&
                (
                    $remoteAddr === '127.0.0.1'
                    ||
                    $remoteAddr === '::1'
                    ||
                    \PHP_SAPI === 'cli'
                )
            ) {
                $return = true;
            }
        }

        return $return;
    }