简单地使用它将工作

   $auth = base64_encode('user:'.config('mailchimp.api_key'));
    //API URL
    $urll = "https://".config('mailchimp.data_center').".api.mailchimp.com/3.0/batches";
    //API authentication Header
    $headers = array(
        'Accept'     => 'application/json',
        'Authorization' => 'Basic '.$auth
    );
    $client = new Client();
    $req_Memeber = new Request('POST', $urll, $headers, $userlist);
    // promise
    $promise = $client->sendAsync($req_Memeber)->then(function ($res){
            echo "Synched";
        });
      $promise->wait();

这对我来说很有效(使用Guzzle 6)

$client = new Client(); 
$result = $client->post('http://api.example.com', [
            'json' => [
                'value_1' => 'number1',
                'Value_group' =>  
                             array("value_2" => "number2",
                                    "value_3" => "number3")
                    ]
                ]);

echo($result->getBody()->getContents());

对于Guzzle <= 4:

这是一个原始的post请求，所以把JSON放在body中解决了这个问题

$request = $this->client->post(
    $url,
    [
        'content-type' => 'application/json'
    ],
);
$request->setBody($data); #set body!
$response = $request->send();

来自@user3379466的答案可以通过设置$data来工作，如下所示:

$data = "{'some_key' : 'some_value'}";

我们的项目需要的是将一个变量插入到json字符串中的数组中，我这样做如下(如果这有助于任何人):

$data = "{\"collection\" : [$existing_variable]}";

因此，与$existing_variable是，说，90210，你得到:

echo $data;
//{"collection" : [90210]}

另外值得注意的是，你可能还想设置'Accept' => 'application/json'以防你碰到的端点关心这类事情。

解决方案$客户端->请求('POST'，…

对于那些使用$client->请求的人，这是如何创建JSON请求的:

$client = new Client();
$res = $client->request('POST', "https://some-url.com/api", [
    'json' => [
        'paramaterName' => "parameterValue",
        'paramaterName2' => "parameterValue2",
    ]
    'headers' => [
    'Content-Type' => 'application/json',
    ]
]);

Guzzle JSON请求参考

$client = new \GuzzleHttp\Client();

$body['grant_type'] = "client_credentials";
$body['client_id'] = $this->client_id;
$body['client_secret'] = $this->client_secret;

$res = $client->post($url, [ 'body' => json_encode($body) ]);

$code = $res->getStatusCode();
$result = $res->json();