IF you're using IIS forget .htaccess files. They can be configured to work with IIS but this must be done by the server admin and most don't want to know. That means the default setup won't work with them.
The only other way to hide your .php extension is to call your files index.php and then put them in unique directories such as:
etc but leave out the index.php part. Sure, anyone can type index.php and successfully pull a page however it will obfuscate this a bit for you.
My helpful sig has gone because a mod below the administrator gave me an infraction - despite the administrator personally agreeing to it.
If you need any php tips or tricks you can PM me.