Google OAuth invalid grant
Fatal error: Uncaught exception 'Google_Auth_Exception' with message 'Error refreshing the OAuth2 token, message: '{ "error" : "invalid_grant" }'' in /includes/Google/Auth/OAuth2.php:330.
A few days of testing, experiments, “googling” Internet, and miscellaneous shamanic dances with a tambourine around “Google APIs Client Library for PHP” source code and the sample example of its usage did not allow me to make even a little step forward. Trying various variants with service-account.php (recreate service account, replacing private key file, trying other, default service account with client secret loading from JSON file) did not help and I still was on the same place with the same error. That was funny to resolve finally this issue and smile to myself, how the small mistake at very begin may cost a lot of time to fix it.
I used Google service account, created especially to for interaction between Google servers. The problem was related to the service account name I used in the code taken from service-account.php example:
Service Account authentication example
When I found “service_account_name” in the example code and at the PHP Google APIs library source code, I remembered that I saw exactly that term somewhere in the Google developer console. The 1st link from Google search on “google app service account name” keywords
Google search app engine service account name
returns me the link to the article
Google App Service Account Name
which shows where to find my Google App project Service Account name – Application Settings at the Google App Engine console:
Google App Engine Service Account Name
This service account name I inserted into my test example. It seems was right search for the right information. But it leaded me to the permanent wrong result:
Fatal error: Uncaught exception 'Google_Auth_Exception' with message 'Error refreshing the OAuth2 token, message: '{ "error" : "invalid_grant" }'' in /includes/Google/Auth/OAuth2.php:330
Problem was gone when I replaced Google App project service account name with the service account email from APIs & AUTH – Credentials page, which is finally the right place to take all the credentials to work with this API:
APIS & AUTH – Credentials
Conclusion: Service account name to use in the Google API PHP library is the email assigned by Google to your new created service account at the Google Developer Console “APIs & AUTH – Credentials” page (look on the screenshot above).
Little advice – if you don’t wish to lose a lot of time struggling with strange errors start your adventure with Google API PHP library from this link. It will help you to make less mistakes than someone other (do you guess who?) already did :).
