Authentication Limited by google apps domain

[Brad Bonkoski]

Hello,

I am using this example: https://developers.google.com/+/quickstart/php

However, I want to only allow people to auth from within a google apps managed domain.

Are there any easy ways to set the domain as a configuration option to restrict public access from using the application?

I'm sure I can go some post processing to filter out people from the outside world, but would be much cleaner and easier if a config option would do this for me.

thanks

-brad