Struggling with "clean urls" - .htaccess

Question

After many hours of researching this site (and google) I've decided I need help with this problem I'm having. I'm using a snippet of code in my htaccess file that allows for a url to be accessed by either including the .php extension (like this www.mysite.com/about.php ), leaving the extension off completely with no slash (like this www.mysite.com/about ), or adding a slash at the end in place of the extension (like this www.mysite.com/about/ ).
So that part works beautifully. However it still shows the .php extension in the address bar after the page loads whether the user inputted it or not. So far I'm pretty happy with what it's doing as is, but I'd really just like to be able to hide the extension and even go so far as to put a slash at the end and for somereason nothing I'm doing is working in that respect. Hopefully some of this made sense.
I currently have this in my htaccess file.
RewriteEngine on
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_FILENAME}\.php -f
RewriteRule ^([^/]+)/$ http://mysite.com/test-server/$1.php
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_URI} !(\.[a-zA-Z0-9]{1,5}|/)$
RewriteRule (.*)$ http://mysite.com/test-server/$1/ [R=301,L]

Answer 1

This is actually a bad approach SEO-wise because your content is accessible via multiple URLs. Either enforce extensions or don’t.
I prefer extension-less URLs as it for some bizarre reason I want to switch technology stack (i.e. to Rails) I’m not stuck with “.php” on the end of my URLs.
To achieve this, you can just rewrite requests for the extension-less request to a script with “.php” on the end. In your .htaccess file place the following:
RewriteEngine on
# redirect to extension-less URL if requested
RewriteCond %{THE_REQUEST} ^[A-Z]+\s.+\.php\sHTTP/.+
RewriteRule ^(.+)\.php $1 [R=301,L]

Answer 2

I also found this bit of code that works for me quite well at removing the extension, but I've only got it working at the root level so far. I'd like to be able to mod it for different directories within my test site since url structure is really important for this particular project. Nothing but errors when I do that though.
AddType text/x-component .htc
RewriteEngine On
RewriteBase /
# remove .php; use THE_REQUEST to prevent infinite loops
RewriteCond %{THE_REQUEST} ^GET\ (.*)\.php\ HTTP
RewriteRule (.*)\.php$ $1 [R=301]
# remove index
RewriteRule (.*)/index$ $1/ [R=301]
# remove slash if not directory
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_URI} /$
RewriteRule (.*)/ $1 [R=301]
# add .php to access file, but don't redirect
RewriteCond %{REQUEST_FILENAME}.php -f
RewriteCond %{REQUEST_URI} !/$
RewriteRule (.*) $1\.php [L]