Guzzle给了我奇怪的json回应

I'm currently using Guzzle to make a post request and send some parameters.

Here's my code:

$client = new Client();
$url = $this->my_url;

$client->setSslVerification(false,false,0);
$request = $client->post($url,null,array(
                            "param1" => $param1,
                            'param2' => $param2
                        ));

$postBody = $request->getBody();
$response = $client->send($request);
$body = $response->getBody();

echo $body;

I get this return (JSON) when I'm doing the echo:

int 1
{"Response":true}

And of course, I can't do a json_decode on it.
I don't understand why I can't do it and why I have this "int 1" before it.

Any ideas about this issue?