Authentication between multiple web applications

I am planning on creating a number of web applications that allows the user to share an account between these applications. I am using apache, php and mysql.

My question is, is it possible for the user to login on one server and then be able to use all the applications with these login details. I was thinking of using some kind of web service/api that can be accessed by the other applica开发者_StackOverflowtions but I am not entirely sure that this is the best way.

Thanks in advance.

You might want to go for the popular OpenID:

OpenID is an open standard that describes how users can be authenticated in a decentralized manner, obviating the need for services to provide their own ad hoc systems and allowing users to consolidate their digital identities.

There is also OAuth authentication system:

OAuth (Open Authorization) is an open standard for authorization. It allows users to share their private resources (e.g. photos, videos, contact lists) stored on one site with another site without having to hand out their credentials, typically username and password.

Yes I would build an authentication service. Then I would register within that service which applications the user can use.