Tree/category view database using PHP
i wan to develop a site using a database in a tree or category navigation sistem. say like a webdierctory which contans data in catogorised way or a e-book download site that is in categorisedd way of data..
How can i design my data base to do in that way? any idea, suggestion or soLid link frOm where i can learn that stretegy? any one help pls??/