public function lookup_consumer($consumerkey) {
        if (strpos($consumerkey, "http://" ) === 0) {
            $consumer = new OAuthConsumer($consumerkey, "secret", null);
            return $consumer;
        }
        if ( $this->consumers[$consumerkey] ) {
            $consumer = new OAuthConsumer($consumerkey, $this->consumers[$consumerkey], null);
            return $consumer;
        }
        return null;
    }