- Configure your server to run everything through the script (e.g., in Apache,
ScriptAlias / /hosts/example.com/htdocs/yourApplication.php
) - Look at
$_SERVER['PATH_INFO']
to determine what the user name is (if there is one). - Use that information to decide if you are going to show a “list of products page” or something else
- Search your database for the appropriate data
You’ll probably find that a lot of MVC frameworks help rather a lot with steps 2 and 3.