Php 向RingCentral API发出的请求

我正在尝试向

RingCentral API

发送请求。指向文档的链接是

https://developers.ringcentral.com/api-reference/Fax/createFaxMessage

如果我没有指定

faxResolution

或

coverIndex

一切正常，传真可以发送。但如果我像下面的代码中那样添加faxResolution参数，我会收到

error“参数[faxResolution]值无效”，“errorCode”：“CMN-101”。

与coverIndex参数相同。我的客户是http 6.3

    $token = $this->ringcentral->platform()->auth()->data()['access_token'];
    $a = array();
    foreach ($destination_numbers as $number) {
        $a[] = [
            'name' => 'to',
            'contents' =>  $number,
            'headers' => ['Content-Type' => 'multipart/form-data']
        ];
    }
    $a[] = [
            'name' => 'faxResolution',
            'contents' => 'High',
            'headers' => ['Content-Type' => 'multipart/form-data']
        ];
    foreach ($attachments as $attachment) {
        $file_pointer = fopen($attachment, 'r');
        $mime = mime_content_type($attachment);
        $a[] = [
            'name' => 'attachment',
            'contents' => $file_pointer,
            'headers' => ['Content-Type' => $mime]
        ];
    }
    $client = new Client();
    try {
        $response = $client->request('POST', url(config('services.ringcentral.app_url')) . '/restapi/v1.0/account/~/extension/~/fax', [
            'headers' => [
                'Accept' => 'application/json',
                'Authorization' => 'Bearer ' . $token
            ],
            'multipart' => $a
        ]);
        $response = json_decode($response->getBody(), true);
    } catch (\GuzzleHttp\Exception\ClientException $e) {
        echo($e->getResponse()->getBody()->getContents());
    }

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以下是RingCentral在使用PHP时的建议。我包括了他们建议的所有内容，但只要看看关于传真分辨率的部分（下降了2/3）

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链接到您在此提出的特定请求的API文档？

    <?php
// https://developers.ringcentral.com/my-account.html#/applications
// Find your credentials at the above url, set them as environment variables, or enter them below

// PATH PARAMETERS
$accountId = '<ENTER VALUE>';
$extensionId = '<ENTER VALUE>';

$recipient = '<ENTER VALUE>';

require('vendor/autoload.php');
$rcsdk = new RingCentral\SDK\SDK(getenv('clientId'), getenv('clientSecret'), getenv('serverURL'));
$platform = $rcsdk->platform();
$platform->login(getenv('username'), getenv('extension'), getenv('password'));

$request = $rcsdk->createMultipartBuilder()
    ->setBody(array(
     'to' => array(array('phoneNumber' => $recipient)),
     'faxResolution' => 'High',
    ))
    ->add(fopen('fax.jpg', 'r'))
    ->request("/restapi/v1.0/account/{$accountId}/extension/{$extensionId}/fax");

$r = $platform->sendRequest($request);
?>