Allowing the usage of custom domain names for web application projects

I would like to know the best way to enable custom domains when creating web applications. For instance, if you look at something like Base Camp, when you sign up for that you create your own 'sub domain' to which you use to login to your basecamp with.

Also, if you look at this like hosted ecommerce sites, you can use your own custom domain instead of using a sub domain of theirs.

Personally I can't see these web applications 'parking' each custom doma开发者_开发知识库in on the web apps hosting account or adding the DNS if it uses a sub domain like Base Camp does.

Therefore, the only way I can think about doing something dynamically like this is to maybe use mod_rewrite to redirect everything to a certain script that does the 'routing' based on the url. Then for the customer domains, the customer would just need to add a CNAME for their domain to something like custom.webappname.com which then in turn gets picked up by mod_rewrite and the php routing file.

If this is the best way forward, are there any performance issues with routing all incoming requests via this 'routing file'?

Sorry if im not clear, tried to explain the best I can.

Yes, your solution would be the best way. That is how other sites do it. Rerouting all requests through a central file using rewrite rules incurs a small performance penalty but it is well worth it.

In fact, in most applications you are already paying that penalty anyway. Any framework that uses the FrontController pattern already does exactly this. This includes pretty much all frameworks like Zend, Symfony 1 and 2, CakePHP, CodeIgniter an many others.

It really depends on the web app your working with.

For example we have a hosted CMS, using the cPanel API we do create an actual hosting account for each customer and install about 50KB of files on account creation including a default template, initial set-up script (handles DB install, initial population of data and basic settings amongst other things) and a few basic front end control scripts such as the contact form, in saying this we don't provide access to the hosting account, all interaction is via our web app. In our case this is regardless if a sub-domain or fully qualified domain. Our customers have the option of self-hosting their domain or we will host it, because we have complete cPanel hosting infrastructure it makes no difference to us where DNS is but if the customer has it away from us it is entirely their responsibility.

The reason we have this hosting set up is so customers can upload their own templates, for disk storage management (we aren't interested in being a file server but customers need some space for PDFs, images, etc) and to make sure the content of 1 customer doesn't get mixed in with the content of another. As a premium paid-for service our lawyers recommended a minimum of separate identifiable folders on the server for file storage.

Another example is blogger/blogspot, it is well known they use mod_rewrite for their sub-domains. This is appropriate for them to do it this way otherwise they would have to create a separate DNS zone for each blog at a minimum and this is a pain (hence why we use cPanel), plus you have all your other virtual hosting set-ups. With mod_rewrite as you will be aware it will use a single wild-card zone to control the sub-domains and the mod_rewrite rule is easy to apply. From there it is simply creating a folder and redirecting requests for the sub-domain to it or directing to the script to control your app depending on what you're doing.

The truth is for an automated system using sub-domains I would use mod_rewrite but for something a bit more complex like a fully blown premium CMS requiring full legal conformity, quota management, suspend, terminate and file removal functions then I would recommend looking at a hosting control panel such as cPanel as a possible solution.

You've got the right idea. You keep a single codebase, running (for the sake of argument) on a single IP. You don't need to worry about virtual hosts, or even mod_rewrite (aside from whatever your application needs).

You web app simply handles any and all requests to that IP (on port 80 or 443, or whatever).

When your application bootstraps in response to a request, it peeks at $_SERVER['HTTP_HOST'], and configures itself for the client associated with that domain name. If not found, it 404s, or whatever makes the most sense.