CODE EXAMPLE FOR PHP

hide extension

RewriteEngine on

#1)externally redirect "/file.php" to "/file"   
RewriteCond %{THE_REQUEST} /([^.]+).php [NC]
RewriteRule ^ /%1 [NC,L,R]
#2)Internally map "/file" back to "/file.php"
RewriteCond %{REQUEST_FILENAME}.php -f
RewriteRule ^(.*?)/?$ /$1.php [NC,L]