Custom script for client area login

I have about 5 clients and I'd like for each client to have his own secure client area/page (where I can upload his/her private documents). Currently using htaccess, I am able to manually assign unique login credentials to each client. This allows them access to a secure directory (but they all have access to this same directory, which is not so ideal). I need it structured so that depending on the username, the login directs the client to his/her personalized page (i.e. Welcome Jim Smith). My Unix-based shared hosting service (Network Solutions) provides SQL, php, and htaccess. I need the client login script to visually integrate into the simple site I designed using xhtml and css: [login to view URL] Also, I need the script to be secure (i.e. no sql injection issues, etc.). The simpler the solution, the better. In other words, if the solution is easy enough that I can install it, that helps. Many thanks in advance for your bid.