Read about HybridAuth - a PHP social login library:
Usually, you need to setup that library on a site to use the social login on that site.
But because I have many sites, I dont want to setup it on every of my sites. I want to concentrate all on only 1 site. We called it site A.
Look at this:
You will see the Loginza widget under the "Sign In also as:" text.
Click "register without filling in the form" to see how it works.
Now, sign up with them, you will get the exact widget to paste to your site. And it will work exactly the same way you see on Loginza.
== Now my requirements ===
I want to setup HybridAuth on site A. From site A, I can generate a similar widget, to copy and paste to every of my sites (B, C, D,...). All data about the visitors (name, email, profile,...) provided by social service, thru HybridAuth, will be recorded and saved only on site A.
I want to have also a member area on site A, where you need to sign in to add and manage the domains which use the widget. Only the domains that you claim and verify in that member area can be allowed to use the widget. So if people copy and paste the code of widget to an unknown domains, it wont work and will be denied by site A. It's UNLIKE Loginza, where the code of widget can be pasted to any domain or site.
I dont really need the exact widget as you see on Loginza, but something that can display the buttons: Login with Facebook, Login with Google,... and the code must be easy to add to B, C, D,... Do it as you can do, I can't tell you how to do it because I simply dont know.
The text displayed on the buttons should be changed easily in the member area, depending on the page where I paste the widget code: Sign up with Facebook, Login with Facebook, Login thru Facebook,... something like that (I think that is easy with CSS or MySQL)
HybridAuth can also help you to post to the Facebook wall, send tweet,... (you should read the HybridAuth docs - read it carefully) and create a module in the member area, where you can, from the member area on site A, post to Facebook, Google Plus,... or send tweet to the account of the user who is just used the social login button on other sites B, C, D,.... If you understand what I mean.
The site should be created with Bootstrap from Twitter, a responsive design so I can visit with my smart phone.
Im open to suggestions.
Help me, I will pay you.