Multiple domain names under one WordPress Installation

This is what I’d like to accomplish, hopefully under one WP install: I would like to use one WP install for my main domain + three subdomains, where subdomains need to be somehow “masked” / add-ons of other domains.

i.e.
www.mymaindomain.com
branch1.mymaindomain.com -> www.differentdomain.com
branch2.mymaindomain.com -> www.completelydiffdomain.com
branch3.mymaindomain.com -> www.anotherdomain.com

More details:

• One main WordPress Website, www.mymaindomain.com
• The homepage has links that take users to three different branches of the website.
• Client wants each branch to have it’s own domain (design and everything are pretty much the same)
• So, clicking on the first branch, should take users to www.differentdomain.com (keep in mind that the design is the same, header, footer, and what not)
• Same thing for the second and third “branches”, they take the user to a different domain, but the UI is the same.

One idea I had is to create subdomains for each “branch” and then create an add-on domain that would point to the subdomain, but this would require installing WP in each subdomain.

Is there a way to handle this (i.e. .htaccess), where subdomain.mymaindomain.com would be masked as www.differentdomain.com?

Thanks!

You need the following:

1) Enable WordPress Multisite in your main domain

• The Ultimate WordPress Multi Site Network Management Guide (tutorial)
• Multisite Rationale (case study, tips, tools)

2) Install the plugin WordPress MU Domain Mapping

• Multisite Domain Mapping Tutorial
• Here’s a workaround to make Domain Mapping work in GoDaddy and Dreamhost shared hosting (may apply to other hosting companies)

After that, you’ll be able to achieve your goal.