protected function curl($uri, $data)
    {
        // Force data object to array
        $data = $data ? (array) $data : $data;

        $headers = [
            'Content-Type: application/json',
            'Accept: application/json',
            'Authorization: ' . $this->apiToken
        ];

        // This is the clickatell endpoint. It doesn't really change so
        // it's safe for us to "hardcode" it here.
        $endpoint = static::API_URL . "/" . $uri;

        $curlInfo = curl_version();

        $ch = curl_init();
        curl_setopt($ch, CURLOPT_URL, $endpoint);
        curl_setopt($ch, CURLOPT_HEADER, 0);
        curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
        curl_setopt($ch, CURLOPT_HTTPHEADER, $headers);
        curl_setopt($ch, CURLOPT_USERAGENT, static::AGENT . ' curl/' . $curlInfo['version'] . ' PHP/' . phpversion());

        // Specify the raw post data
        if ($data) {
            curl_setopt($ch, CURLOPT_POST, 1);
            curl_setopt($ch, CURLOPT_POSTFIELDS, json_encode($data));
        }

        $result = curl_exec($ch);
        $httpCode = curl_getinfo($ch, CURLINFO_HTTP_CODE);

        return $this->handle($result, $httpCode);
    }