如何通过PHP安全地检索谷歌用户ID？

Question

I'm trying to set up a system that a user could sign up through google sign-in and I need a detail about a user that will always be constant. I figured that would be the ID, but that's pretty much the only detail I can't get through PHP.

I can get the details about a user using a token ID and it would return this.

"iss": "https://accounts.google.com",
 "sub": "110169484474386276334",
 "azp": "1008719970978-hb24n2dstb40o45d4feuo2ukqmcc6381.apps.googleusercontent.com",
 "aud": "1008719970978-hb24n2dstb40o45d4feuo2ukqmcc6381.apps.googleusercontent.com",
 "iat": "1433978353",
 "exp": "1433981953",

 // These seven fields are only included when the user has granted the "profile" and
 // "email" OAuth scopes to the application.
 "email": "[e-mail]",
 "email_verified": "true",
 "name" : "Test User",
 "picture": "https://lh4.googleusercontent.com/-kYgzyAWpZzJ/ABCDEFGHI/AAAJKLMNOP/tIXL9Ir44LE/s99-c/photo.jpg",
 "given_name": "Test",
 "family_name": "User",
 "locale": "en"

But I can't find a detail that would be unique and constant so I can see if their account already exists. Is there something else I could use or can I retrieve the ID of a user through php?

Answer 1

I'm not sure about the labels above or where you got them, but looking at the values (and comparing them to my own collection of Gmail User IDs from Oauth), the sub value is the user ID field.

Counterintuitively, email is not unique, as in one account can have several email aliases, and you can change email addresses on an account.