dropdown list box problem

hello friends

I am a begginar of php.
i am using two dropdown listbox on one page.
both are bind dynemically.
when user select into first dropdown the accorging to first second will fill.
My problem is that after fill second first will set to '0' select mean set to ' Select a Item'

please help me how to do this


send me appropiate solution.

thanks

How is the second listbox filled? Do you refresh the page to go out and grab the data for the second listbox using PHP?