facebook-twitter like login system in php
<p>I have 2 websites with a member login system.</p>

<p>Members are registered at one website.</p>

<p>I want that all members registered at website "A", should not need to register at websites "B".
By using the credentials at website "A", members should be able to login at website "B".</p>

<p>It also should be in a secure way.</p>
