Honestly, its only four pages, don't think you need to go php.
please ignore this advice,
plan on expansion,
plan on 100,000 pages, and the database to support them, and the design features to import a single css and javascript file, and to php/ssi/cgi/asp(your choice) include all the common code.
Do it now when it
is four pages, and you dont have to come back in a month and rewrite 40, come back in six months to rewrite 400 or more, and decide what code can be common.
imagine for example Wikipedia without the includes, and backend, every page requiring Joe Public to hand code menus to millions of other pages, for a minor edit .....
Dont think anyone would like to make edits
( WikiPedia is chosen as a design model that
works )