Facebook is some of the worst aspects of the Web, but that's where the users are. So, you might want to integrate.
General PHP Integration
The Facebook PHP SDK v4 https://github.com/facebookarchive/facebook-php-sdk.git is available to integrate your PHP application with Facebook.
Drupal Facebook integration
The old Drupal module 'fb' is no longer maintained.
todo replace the fb module. See https://www.daymuse.com/blogs/drupal-facebook-login-connect-integration-tutorial