Cascading Drop Down List System

Looking at producing some website functionality the same as can be found here:

As you choose an option in a drop down list, the next list populates with only the information relevant, and so on down the list, with the results listed on a results page, with links to the narrowed down products.

I’ve been told so far that “Use Javascript to do Ajax calls back to the server to request the information, that will then be displayed in those drop downs.”

Any suggestions/pointing in the right direction is much appreciated.

When listing main menu , you can get it’s ID and use javascript to to call php function , to retrieve any sub menu which it’s parents ID is main menu ID . Sorry I’m not good at explaining things.

Wordpress menu is a good example if you want to study about it.