How to hide part of a string from a URL?

Question

Apache HTTP Server

Good afternoon!
Tell me, please, how from the line of the form:
http://site.ru/projects/aplication.php
Hide (just hide) the end /projects/aplication.php?
So that the address bar is displayed simply http://site.ru, so as not to burn the form handler file once again.
Tried like this:
RewriteEngine On

RewriteRule ^(/projects/aplication.php)$ $1.php [NC]

Gives an error message.