My friend has created a website and each registered user has its own blog, which can be accessed by www.hisWebsite.com/username. Of course, the blog has several pages such as blog.php, photo.php, video.php.

It's just very much like the xanga.com.

As you can imagine, each user can access his blog with these addresses:
www.hisWebsite.com/username/blog.php
www.hisWebsite.com/username/photo.php
www.hisWebsite.com/username/video.php

Currently, in his design, whenever a user registers, a new folder named by the user's username will be created under the web document root and these 3 pages will also be copied to that folder.

It's an interesting design, because every folder has exactly the same 3 pages. If we need to change the blog a little bit, all these pages will need to be updated.

So, I'd like to know how we can allow the users to access their blog with this pattern of address:

www.hisWebsite.com/username/

,but without creating a folder for each user, for keeping the same set of pages.

Many thanks to you all.
I'd like to add that, the web hosting is not on his computer.
He may not be able to alter some settings of the web server.