Google-api-php-client: How to get OAuth 2.0 access token for Firebase Cloud Messaging HTTP v1 API

[andreszs]

The FCM HTTP V1 API requires the server to get a "short-lived OAuth 2.0 access token" to use as the Authorization: Bearer=TOKEN request header. To do so, the docs simply point in the direction of this API Client Library, and they show some examples for the Node and other non-PHP languages:

After exploring the present google-api-php-client library, I can't find any possible way to get this token. There are mentions to OAuth 2.0 and tokens in many places, but there isn't a simple example or explanation on how to get an OAuth 2.0 access token for use with FCM HTTP V1 requests.. That is all I need to get to continue with my own PHP-based curl() implementation of the FCM API.

If google wants developers to migrate to the HTTP v1 API, this process should be clearly explained in a simple example in the very home page of the PHP client library.

Does anyone know how to get such token with this library? Is it even possible? Thanks in advance.

[jdpedrie]

You may use either of the following methods to obtain an access token:

putenv('GOOGLE_APPLICATION_CREDENTIALS=/path/to/keyfile.json');
$scope = 'https://www.googleapis.com/auth/analytics.readonly';
$client = new Google_Client();
$client->setScopes($scope);
$client->useApplicationDefaultCredentials();
print_r($client->fetchAccessTokenWithAssertion());

use Google\Auth\CredentialsLoader;

$scope = 'https://www.googleapis.com/auth/analytics.readonly';
$credentials = CredentialsLoader::makeCredentials($scope, json_decode(file_get_contents(
    '/path/to/keyfile.json'
), true));

print_r($credentials->fetchAuthToken());

If you are not using the API Client for anything besides obtaining an access token, I suggest the latter, as it only requires installation of google/auth, allowing you to drop the much larger dependency on google/apiclient.

If you wish to call Firebase Cloud Messaging via the PHP API Client, you can allow the client to authenticate on your behalf similarly to the first example:

putenv('GOOGLE_APPLICATION_CREDENTIALS=/path/to/keyfile.json');
$scope = 'https://www.googleapis.com/auth/analytics.readonly';
$client = new Google_Client();
$client->setScopes($scope);
$client->useApplicationDefaultCredentials();

$fcm = new Google_Service_FirebaseCloudMessaging($client);
// construct and execute API requests, will be authenticated using the service account.

[jdpedrie]

I'm going to close this issue out. If you're still having trouble, please feel free to re-open!