Having .php extensions

Hiya

I have a client who wants to use wordpress for his exsisting website. Currently his website is made up of files with .php extensions (eg. websites.com/about.php) and he wants to keep the urls as they are.

Is there a plugin or anything that allows the slug to include .php at the end? I tried adding a test page called test.php but wordpress automatically renamed it test-php

He doesn’t want to use URL re-writes.

Any suggestions would be greatly appreciated.

Thanks,
Emma