function base64url_encode($plainText) {

            $base64 = base64_encode($plainText);

            $base64url = strtr($base64, '+/=', '-_,');

            return $base64url;

        }

        function base64url_decode($plainText) {

            $base64url = strtr($plainText, '-_,', '+/=');

            $base64 = base64_decode($base64url);

            return $base64;

        }