Pointing a domain to a subscription based web-app?

I'm about to start building a subscription based website that will function much like 37signals offerings in terms of users paying a monthly fee to use the site.

But in my case I would like for th开发者_开发问答em to be able to use their own hosted domain names and have them point to my server.

Is this possible? How do i link up the domain name with their account on my server?

Thanks a mil!

EDIT: This site will be made using PHP

This should be possible.

You need to get the user to setup a A record or CNAME record to point their domain name to you server.

You haven't said what language you are developing the site, but most languages should let you find out the requested host, eg in PHP you would use $_SERVER['HTTP_HOST'] which would return the request domain.

You can then use this to customise the experience appropriately.