Site Redesign / Page Rename

Hello

First of all, Merry Christmas to members..

We are redesigning client’s existing website that has about 100+ static (html) pages… at the moment to use the common elements like top menu, footer menu or say left menu.. we used JavaScript to create one file so if any changes are there we can update JavaScript file only and doesn’t have to edit each of the page for small change.. as we know that google doesn’t crawl JavaScript so we are losing valuable crawler activity..

Now in new design.. there are two options we can think of..

1. create site in php, so we can use php include to include those common elements
2. use shtml.. and then using htaccess we can convert it to show as html files

Now we think of php site at the moment., so i would like to know your valuable comments for the following queries

1. is there any difference in crawling html site vs php site
2. google has indexed lots (almost all) our pages as html (as per existing site).. now if we change page name + extension .. do we have option to redirect html to php (permanent) if yes.. please let me know how ?
3. .. finally let me know any other complication that i might not seen at the moment

Waiting for your reply..

Thanks & regards
Kashyap