private function refreshAccessToken() {
        // Setup the params
        $params = [
            'client_id'     => $this->clientID,
            'client_secret' => $this->secret,
            'grant_type'    => 'refresh_token',
            'refresh_token' => $this->refreshToken
        ];

        // Parse the cURL result
        $this->parseAccessToken(CURL::post($this->url, $params));
    }