Abraham\TwitterOAuth\TwitterOAuth::oAuthRequest PHP Method

    private function oAuthRequest($url, $method, array $parameters)
    {
        $request = Request::fromConsumerAndToken($this->consumer, $this->token, $method, $url, $parameters);
        if (array_key_exists('oauth_callback', $parameters)) {
            // Twitter doesn't like oauth_callback as a parameter.
            unset($parameters['oauth_callback']);
        }
        if ($this->bearer === null) {
            $request->signRequest($this->signatureMethod, $this->consumer, $this->token);
            $authorization = $request->toHeader();
        } else {
            $authorization = 'Authorization: Bearer ' . $this->bearer;
        }
        return $this->request($request->getNormalizedHttpUrl(), $method, $authorization, $parameters);
    }