laravel http客户端文件上传 

        //方式一：直接用laravel自带的http客户端，一行搞定
        $response = Http::withHeaders($headers)->attach('file', fopen($file_dir, 'r'))->post($url, ['meta' => $body_json]);
        //方式二：用GuzzleHttp客户端，其实方式一也是封装了GuzzleHttp，但更加便捷。
        $client = new Client();
        $r = $client->request('POST', $url, [
            'headers' => $headers,
            'multipart' => [
                    'name'     => 'file',
                    'contents' => fopen($file_dir, 'r'),