.htaccess mod_rewrite doesn't work - php

Question

I have an .htaccess file in my directory where I'd like to change about-us.php to /about-us/ and I have used mod_mod_rewrite generator to do so however either I get 500 internal server errors or it doesn't work. So I checked my apache and its already enabled as default - I also have confirmed this is enabled using
/usr/local/apache/bin/httpd -l | grep rewrite
and I get
mod_rewrite.c
but this is it, my server is centos 6
I really don't know what else I need to do, do you guys have any idea? code below is another try but even this doesn't work fine
RewriteEngine On
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_FILENAME}\.php -f
RewriteRule ^(.*)/$ /$1.php
Many thanks in advance

Answer 1

http://httpd.apache.org:
In general, .htaccess files use the same syntax as the main
configuration files. What you can put in these files is determined by
the AllowOverride directive. This directive specifies, in categories,
what directives will be honored if they are found in a .htaccess file.
If a directive is permitted in a .htaccess file, the documentation for
that directive will contain an Override section, specifying what value
must be in AllowOverride in order for that directive to be permitted.
http://httpd.apache.org/docs/2.2/mod/core.html#allowoverride
<Directory /var/www/>
AllowOverride All
</Directory>

Answer 2

As #ava points out, make sure your Apache server is set to allow directives at the directory level via htaccess. It appears that your rewrite rule is backwards. You state that you want to redirect from files (about-us.php) to a directories (about-us) but your rule is set up for the opposite.
If you're just rewriting one file, do so explictly.
Rewrite On
# Rewrite specific file (not case sensitive, stop processing rules).
RewriteRule about-us.php about-us [NC,L]
Or, you can remove .php from all files. The following reverses the answer given here.
RewriteEngine On
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule (.*).php $1 [NC,L]
Also consider where the URLs are in relation to the web root and where your htaccess file is (see RewriteBase). If this is a permanent redirect, you should let bots know with [R=301].