How to create sub domain with PHP script?

[Komonko]

Hi Everyone,

I am developing a web project at the moment and i wonder about something.

In my project, visitors will sign up with a username and my PHP script will open a sub-domain for their usernames.

For example, exampleusername.mysite.com should be opened by PHP script upon sign up.

How can i do this? What are the files that i need to modify with PHP script?

Thanks for your help.