Subdomains

[rushenas]

Hi all
How weblog sites create subdomains for their users on fly? I mean when you sign up in weblog systems, if you choose rushenas as your username, then they give you an address like this: http://rushenas.weblog.com. Sure they will keep their user details in a database, but how they give them such URL?

[Weedpacket]

By configuring their server to map the URL to the appopriate directory tree.

[rushenas]

But how they configure their servers?

[MarkR]

They may use wildcard DNS, or update the DNS to add extra host names for those users.

Then they probably run a default virtual host which points all these host names to the same directory.

Inside this directory, a server-side (e.g. PHP) web application, reads the "Host:" header and then modifies its behaviour accordignly.

For example, in PHP you'd get this with $_SERVER['HTTP_HOST']

Mark