to generate sublist each time from database

[sandhya]

hi all,i think my post may not completely related this type.but i'm trying to do this in javascript except data collection from the database. is it possible? if yes how? and my problem is here.

i have a form that displays main categories from database in a drop down list. after selecting a category a drop down list should be generated with the sub categories of the selected category. these sub categories also may have the sub-subcategories. if exists, another drop down list should be generated with  the sub-subcategories of the selected subcategory. this process should continue till any selected sub category has no sub-subcategories. how can i do it. i'm developing this form using php and javascript. i"ll be thankfull to whom can give me the solution.