Saving facebook id as int or varchar?

Question

My question is more advisory than technical. I\'m writing a Facebook app in which I am fetching some information about the user, including facebook_id.
I was wondering i

Answer 1

To quote facebook's upgrade notes regarding graph API v2.0 (effective May 2015):

All IDs are strings. In v1.0, IDs were often large numbers.

Which (to me) implies that userids are not guaranteed to be numbers. In fact, facebook recommend that you use strings:

https://developers.facebook.com/docs/graph-api/reference/v2.2/user#fields

Name:id
Description: id The id of this person's user account.

This ID is unique to each app and cannot be used across different apps(...)

type: string

Although I must admit I've never seen an alphanumeric id.