Multi-site login bar
<p>How does one implement a multi-site login bar?  I am starting a personal project that would require a header bar above multiple sites that allows users to login or do other things, I am coding this in PHP and have not been able to find anything online other than wordpress plugins.</p>

<p>EDIT: Sorry I wrote this late last night so I was very vague about it. I'll go into a bit more detail.</p>

<p>An example would be the StackExchange bar at the top, I will have one unified login database that each site will access.  </p>

<p>I guess I just am curious how best to implement this via PHP or some MVC framework.</p>
