google oauth 2.0 php api身份验证失败:“使用未定义的常量stdin”[重复]

我正在尝试实现 PlaylistItems: insert YouTube Data API sample ,当我尝试运行它时,我得到以下信息:

通知 :使用未定义的常量stdin-在中假定为“stdin” /示例/path/to/script.php 在线 五十一

包含此行的函数不清楚stdin从何处获取其值:

function getClient() {
  $client = new Google_Client();
  $client->setApplicationName('API Samples');
  $client->setScopes('https://www.googleapis.com/auth/youtube.force-ssl');
  // Set to name/location of your client_secrets.json file.
  $client->setAuthConfig('client_secrets.json');
  $client->setAccessType('offline');

  // Load previously authorized credentials from a file.
  $credentialsPath = expandHomeDirectory(CREDENTIALS_PATH);
  if (file_exists($credentialsPath)) {
    $accessToken = json_decode(file_get_contents($credentialsPath), true);
  } else {
    // Request authorization from the user.
    $authUrl = $client->createAuthUrl();
    printf("Open the following link in your browser:\n%s\n", $authUrl);
    print 'Enter verification code: ';
    $authCode = trim(fgets(STDIN)); // <--- Appears to be the problem

    // Exchange authorization code for an access token.
    $accessToken = $client->fetchAccessTokenWithAuthCode($authCode);

    // Store the credentials to disk.
    if(!file_exists(dirname($credentialsPath))) {
      mkdir(dirname($credentialsPath), 0700, true);
    }
    file_put_contents($credentialsPath, json_encode($accessToken));
    printf("Credentials saved to %s\n", $credentialsPath);
  }
  $client->setAccessToken($accessToken);

  // Refresh the token if it's expired.
  if ($client->isAccessTokenExpired()) {
    $client->fetchAccessTokenWithRefreshToken($client->getRefreshToken());
    file_put_contents($credentialsPath, json_encode($client->getAccessToken()));
  }
  return $client;
}

请原谅我的幼稚,但是脚本应该如何提供身份验证代码?为什么不执行此步骤?