public function getSignableParameters()
    {
        // Grab all parameters
        $params = $this->parameters;

        // Remove oauth_signature if present
        // Ref: Spec: 9.1.1 ("The oauth_signature parameter MUST be excluded.")
        if (isset($params['oauth_signature'])) {
            unset($params['oauth_signature']);
        }

        return Util::buildHttpQuery($params);
    }