private function encodeBearer ($consumer_key, $consumer_secret){

        // Create Bearer Token as per Twitter recomends at 
        // https://dev.twitter.com/docs/auth/application-only-auth
        $consumer_key = rawurlencode($consumer_key);
        $consumer_secret = rawurlencode($consumer_secret);
        return base64_encode($consumer_key . ':' . $consumer_secret);

    }