public static function generateWithCustomAlphabet($customAlphabet = '0123456789ABCDEF', $tokenLength = 32) {

        // Set initial alphabet.
        $generator = new RandomStringGenerator($customAlphabet);

        // Change alphabet whenever needed.
        //$generator->setAlphabet($customAlphabet);
        // Call method to generate random string.
        $token = $generator->generate($tokenLength);

        return $token;
    }