private function httpClient()
    {
        if (!self::$httpClient) {
            self::$httpClient = HttpClient\CurlClient::instance();
        }
        return self::$httpClient;
    }
private function httpClient()
    {
        if (!self::$httpClient) {
            self::$httpClient = HttpClient\CurlClient::instance();
        }
        return self::$httpClient;
    }
private function httpClient ( ) { if ( ! self :: $ httpClient ) { self :: $ httpClient = HttpClient \ CurlClient :: instance ( ) ; } return self :: $ httpClient ; }
If needed create, and return a http client

@return HttpClient\CurlClient
If needed create and return a http client