微信小程序获取手机号码 phonenumber.getPhoneNumber 提示47001错误

微信小程序获取客户端手机号码，踩的坑。如下提示：

{"errcode":47001,"errmsg":"data format error hint: [6kMDxSDNRa-hAwqia] rid: 6308d1b5-69935bc9-1d99d19f"}

protected function getPhoneNo($code): string
    {
        try {
            $accessToken = $this->getAccessToken();
            if($accessToken) {
                //POST https://api.weixin.qq.com/wxa/business/getuserphonenumber?access_token=ACCESS_TOKEN
                $client = new Client();
                $url = config('mini.get_phone_number');
                $req = $client->post("$url?access_token={$accessToken}", [
                    'json' => [
                        'code' => $code
                    ]
                ]);
                var_export($req->getBody()->getContents());
            }
        } catch (\Throwable | \Exception $e) {
            return $e->getMessage();
        }
    }

这里需要注意的是，post请求时，格式需要用json格式，不能用body格式，即：

正确：

'json' => [
    'code' => $code
]

错误：

'form_params' => [
    'code' => $code
]