yii2：致命错误：未捕获SoapFault异常：[8]数组到字符串转换

Question

这是我的客户肥皂api：

         $client = new SoapClient('http://sabapal.ir/sabapal/frontend/web/apit/PaymentRequest?WSDL', array('encoding' => 'UTF-8'));

        $result = $client->PaymentRequest(
                array(
                    'Amount' => 1000,
                )
        );

这是我的肥皂服务器：

    public function PaymentRequest($Amount)
{

    \Yii::$app->response->format = \yii\web\Response::FORMAT_XML;
    $xmlValues = ['test1' => 'value1', 'test2' => 'value2'];
      return $xmlValues;
}

我有这个错误：

Fatal error: Uncaught SoapFault exception: [8] Array to string conversion in /home/sefroweb/domains/sefroweb.com/public_html/wp-content/plugins/zarinpal-paid-downloads/zarinpalpaid-downloads.php:2890

我不想更改客户端soap api

我只想更改public function PaymentRequest