OAuth Facebook - where to look for information?

Question

PHP

Good afternoon.
Actually the question is:
Where can I find information on the method of authentication using facebook.
For all the social networks I need. networks, wrote a class that requests and receives the necessary data for authentication.
With Facebook, I don’t understand, they offer to download the SDK that no one needs, but I didn’t find instructions, as we say, in VK.

Answer 1

https://developers.facebook.com/docs/ everything is there

Answer 2

https://developers.facebook.com/docs/facebook-logi...
https://developers.facebook.com/docs/php/gettingst...

Answer 3

Look at this lib. There are providers for everything. Works exceptionally well. Working with her is very easy.
hybridauth.sourceforge.net