I have completed the "Quickstart for PHP" but the file (document.gdoc (I have even tested named the file document.txt as in the example) which is in the root of my Google Drive) doesn't get updated as the sample shows. I'm getting code 4 followed by a sort of API code (60 characters long) after I have accepted the request. Everything looks fine in Google Cloud Console and I have inserted my client ID, client secret, and the redirect URI in the sample code.
Have I done something wrong?