How do I merge user accounts when I use Login with Facebook, Google or Twitter?

Question

In my website I have put up Login with Google, Login with Facebook and Login with Twitter.

But if the same user logs in using different providers, ie. the user first logs in using Facebook and then logs out and then logs in using Google I need to identify that both are the same person.

Currently what I am doing is that if the Facebook and Google accounts has the same email id I combine the accounts. The problem is that if the user is logging in using Twitter I wont be getting their email Id which means I cant uniquely identify them.

Does anyone have any other solution ? Thanks

Answer 1

You might consider linking users fb,gmail or twitter to a local db on your site,

Alternate method

Whenever user logs in using any method generate a userid generated from your mysql db and save to a cookie, next time user logs in via any method retrieve the ip and cookie details and update your mysql database accordingly. Next time user logs in , your system will know about their particulars.

Hope it helps.