CodeIgniter is a simple and lightweight PHP framework used to create powerful web applications. Today, we are going to do something nifty: we'll combine user names and subdomains to make for a more cohesive user experience. If you're a bit confused, this feature allows your users to access their accounts by typing in a custom url, which maps to their user name, such as harbinger.yourapp.com.

Their setup shows the homepage for the application if you go directly to the domain but changes to a login form when you hit the subdomain. There's a bit of DNS configuration involved to get the subdomains working (you'll have to add in a wildcard to catch the subdomains). They show you how to set this up on your localhost if you're working on OSX or Windows. With a few changes to the Apache server for virtual host and a basic install of CodeIgniter, they get started creating the database tables and control panel application.

CI's default folder structure is really geared towards one site domain, and having both the application folder and the system folder visible to the browser is not exactly a secure approach. By configuring your install to support multiple sites, not only do you make the updating of the CI core easier, but also make the CI install more secure as a whole.

The example is on a Windows system, but the instructions are generic enough to work on any platform. They're using it under a XAMPP install, but the changes are all below the document root of that setup. You'll need to edit some of the config files and be able to update the Apache configuration to work with VirtualHosts

They haven't gone to far, though - as you'll notice, there's now a "Jobs Feed" on the sidebar that you can subscribe to and get the latest jobs posted with us. This number is growing more and more every day, so it's a great place to keep up with. We've also moved them over to their own subdomain, jobs.phpdeveloper.org to keep things nice and tidy.

From here on out, if you want to find out about the latest job openings, you'll need to subscribe to the new jobs feed or check out the new subdomain, jobs.phpdeveloper.org to keep up with the latest postings. We'll still post the weekly summaries here in the main feed each Saturday for those that just want the overview.

This is really handy for those of us who have the same code handling multiple sites or multiple sub-domains. A case in point: When I coded NetBoardz (my free forum hosting service now defunct), I had one codebase handling all 250 forums. How? Simple. When the code runs, it determines which site the user is loading and does different things (like using different databases) dynamically.

He shows the two key points to dividing things up - grabbing the domain and subdomain they were trying to access. This can be fed into a script that can switch things like layout or even functionality based on which site they've chosen.