said by Ashke:
Ok... If you are using the very very basic language, HTML...
If he's using a "very very basic language, HTML", why give him a PHP "solution"? PHP is just adding an additional layer of complexity where it's not needed, and may not even be an option.
The three most dominate web servers (Apache, nginx, IIS) have ways of handling extensionless URLs that I think most would consider better solutions then a PHP page acting as a proxy.
The main reasons for extensionless URLs SEO, appearance, and technology agnostic. SEO is arguable as to it's importance, and using a ugly URL is almost universally regarded as a better idea than serving up content specifically based on query string. Appearance is pretty obvious, and a query string is always uglier than just about anything else. And as far as not being tied to one technology or another by not having an extension, I don't think that's really an issue there with this particular site.
Create a folder entitled "contactus" (if you are using linux or unix distros, then I strongly recommend you to keep it all in lowercase because the Unix/Linux are pretty inane when it comes to case-sensitivity)
Unix/Linux are the operating systems and have nothing to do with serving up files. And I'd argue that the *nix webservers (Apache, nginx, and similar) are are the opposite of inane when it comes to case sensitivity. index.html is different than InDeX.HtMl. It's IIS and servers that have case-insensitivity enabled that dumbly serve up files regardless of case.