PHP/Javascript

This is what my screen looks like:

                                  I want to order ...
description     image    dropdown box              @ 7.95 each = [text box]
                                  containing 0-20
                                  numerics

I had been contemplating using Javascript to perform the text box extension of the quantity * rate calculation. However, the need is to also update a MySQL table with the session tracking number and other pertinent information about the selection so a purchase order can be written in a subsequent module. Can this be done with straight PHP or will it require a mix of Javascript for the calculation and PHP for the data base update? If so, what might the code look like? Bob