问为了将用户数据发布到应用程序接口，应该在哪里定义xhr.send？

EN

    <?php

  $postData = file_get_contents("php://input");
  $request = json_decode($postData);

  header('Access-Control-Allow-Origin: *');

echo json_encode(isValid($request->captchaResponse));
exit;

function isValid($response) {
    try {
        $url = 'https://www.google.com/recaptcha/api/siteverify';
        $data = [
            'secret' => 'mykeyishere',
            'response' => $response
        ];

        $options = [
            'http' => [
                'header'  => "Content-type: application/x-www-form-urlencoded\r\n",
                'method'  => 'POST',
                'content' => http_build_query($data)
            ]
        ];

        $context = stream_context_create($options);
        $result = file_get_contents($url, false, $context);
        return json_decode($result);
    }
    catch (Exception $e) {
        return null;
    }
}

?>