integrate login to my sites with OpenId or OAuth

Question

i have a few site developed with zend framework 1 and zend framework 2,i wanna users register in main site and in other sites i want to have a login button ,if user click on login: 1- if user logged in in main site ago , user login without enter any information. 2- if user not logged in in main site a popup open and ask his username/password of main site ,then login to site. i don't understand is that possible with OpenId or OAuth. in OpenId user must generate a OpenId Id for example:

http://www.example.com/USERNAME

but i prefer user don't enter any additional information.

for example in the Stackoverflow you can use Google or Yahoo account. if you wanna use yahoo account it asked your OpenId,but i don't know what system Google use that it not asked for any id and just user enter his email and password if is not logged in to his Google account, I prefer Google System that user do not enter any Url to login. sincerely

Answer 1

Clicking the Google button on the Stackoverflow login screen secretly fills the URL

https://www.google.com/accounts/o8/id

as OpenID URL. This is an XRDS file which tells the OpenID library where the auth server can be found.

The OpenID spec defines this in section 7.3.1:

If the end user entered an OP Identifier, there is no Claimed Identifier. For the purposes of making OpenID Authentication requests, the value "http://specs.openid.net/auth/2.0/identifier_select" MUST be used as both the Claimed Identifier and the OP-Local Identifier when an OP Identifier is entered.