I want this magic directory

I just want every customer on my site get his own unique id as his directory name but the pages requested are all processed by the root. Such as: customer1's url is http://www.mysite.com/2000123/ customer2's url is http://www.mysite.com/2000124/ ^^^^^^^UID and the pages requested are actually processed by http://www.mysite.com/ I want it to implement security and personalization. I don't want to use .php?uid=XXX because of lazy. :) thanks.