I want a login & registration functionality like [url removed, login to view]
(open id based). In this, I would also like to add login via twitter.
The code you give should be easy to integrate in any website. You should give me a one-liner code, that I can use to display the login windows/buttons on any part of my website (for example while commenting).
The websites that I will be using this are written in PHP, if that matters.