I call programming php and other major languages software in my eyes. and you can write a piece of script or (software) coding in php that will accomplish this.
I have personally done it before, it's mostly use of mod-rewrite and dynamic directories or sub-domains that can contain generated html or (whatever extension) files that will upon loading redirect properly not 303 or 404, it will look as real as your domain but redirected by a script.
So example:
typing in
http://www.yoursite.com/chris
would redirect to whatever I want, while keeping the domain in the address bar showing at all times
http://www.yoursite.com/chris
or sub-domain: chris.yoursite.com