Where can I find the Google+ API?

I am planing to write some apps with Google+开发者_StackOverflow中文版. Where can I find its API?

It's up:

http://developers.google.com/+/api/

There's no public API yet. You can sign up to get notified on developments:

https://services.google.com/fb/forms/plusdevelopers/

There is no public API at the moment. You can sign up here to get more information when it is available.

Google: http://developers.google.com/+/api/ Free Google Plus API eBook: http://www.heronote.com/files/Google-Plus.htm

Use following link: Google Plus API Implementation in PHP.