在这里，您可以看到我有两个参数，分别是state和code。
下面是一个来自google-ads-php源代码的例子（打开链接查看完整的例子/代码）：

// Exit if the state is invalid to prevent request forgery.
$state = $request->getQueryParams()['state'];
if (empty($state) || ($state !== $oauth2->getState())) {
    throw new UnexpectedValueException(
        "The state is empty or doesn't match expected one." . PHP_EOL
    );
};

// Set the authorization code and fetch refresh and access tokens.
$code = $request->getQueryParams()['code'];
$oauth2->setCode($code);
$authToken = $oauth2->fetchAuthToken();

$refreshToken = $authToken['refresh_token'];
print 'Your refresh token is: ' . $refreshToken . PHP_EOL;