为什么在此json请求中出现错误？

这是我的功能：

   function transaction_create($wallet_id, $passphrase, $payment_address, $payment_amount, $metadata = array()) {
    
        $api_host       = "";
        $api_user       = "";
        $api_pass       = "";
        $api_url        = "/v2/";
        $api_endpoint   = "wallets/" . $wallet_id . "/transactions";
    
        // post body
        $transaction    = array(
            "passphrase"        => $passphrase,
            "payments"          => array(
                                    "address"   => $payment_address,
                                    "amount"    => array(
                                                    "quantity"  => $payment_amount,
                                                    "unit"      => "lovelace"
                                                    ),
                                    ),
            "metadata"          => $metadata,
            "time_to_live"      => array(
                                    "quantity" => 10,
                                    "unit" => "second"
                                )               
        );
    
    
        $curl = curl_init('https://' . $api_user . ":". $api_pass . "@". $api_host . $api_url . $api_endpoint);
        curl_setopt($curl, CURLOPT_HTTPHEADER, array('Content-Type: application/json'));
        curl_setopt($curl, CURLOPT_POSTFIELDS, json_encode($transaction));
        curl_setopt($curl, CURLOPT_RETURNTRANSFER, true);
    
        $api_response = curl_exec($curl);
        curl_close($curl);
    
        // $api_response - available data from the API request
        return $api_response;
    
    }

这是有关api的文档：

https://input-output-hk.github.io/cardano-wallet/api/edge/#operation/postTransaction

给我带来问题的部分是格式化“付款”数组。我的功能的结果是：

“ {” code“：” bad_request“，” message“：” $。payments中的错误：解析NonEmpty失败，预期为数组，但是遇到了对象“}”

然后，如果我创建一个类并将“付款”转换为真实的对象，则会得到相反的错误，它需要一个数组而不是对象... ?? !! ?? 我很困惑。