Multiple websites from one instance, possible?

We're looking to create a number of websites that share the same user database, is there an easy way to do this?

Actually, I was looking for a similar concept. I have 3 domains, I'd like to make these sites unique as far as the feel and look is concerned, but behind the scene, I'd like for all these website to point to only ONE database, so I can only maintain one database regardless how many domains I am using..

Please note, I am using the same concept on some of my sites (see links below), but I am using Coldfusion, not PHP. In Coldfusion, all I have to do is use the same Data Source Name (ODBC) on any website I want to.

Here is an example: These are totally different websites, but notice the ArticleID, they are the same on both sites: 10641 - which means the same data is being pulled from the same database:

http://www.moroccousa.com/news/Headlines/ViewArticle.cfm?ArticleID=10641

http://www.marocpost.net/news/Headlines/ViewArticle.cfm?ArticleID=10641

A.J.