using php you can make dropdowns dynamic in many ways, (1) using java script+php, (2) using only and only php, (3)using php+ajax+javascript.
here is an example, pls check it and give your feed back or further modification about this topic.

you have need two files and sql databases

i have attaches one ajxdrop.txt for the ajax code to get data and state.txt for creating the options in drop down from sql databases. pls copy and paste the two text files in dreamviwer or any editor or make the php files and import the three sql files.

this topic help you to create selection drop down, e.g if you select himachal from first dropdown then it give you option to select its cities then if you select city mandi then it gives you option to select its villages, and same case for all states.