Class to Encapsulate a Reusable Form

I'm developing some reservation forms for a variety of events that all
contain common contact and billing info fields. There are also several
fields pertaining to each specific event. My initial thought was to use
include files to handle the common fields... one for the contact fields, one
for the contact field validation, one for the billing fields, and one for
the billing field validation. Would it be better to implement this using
include files for the presentation of the fields and classes for the
validation/processing of the fields? Just curious as to peoples' thoughts
about how to best implement these forms using php as I come from an asp
background...