trailing slashes in 301 redirect - apache

Question

I've tried to look through the multiple mod_rewrite questions, so I apologize if this is a duplicate.
I'm trying set it so that if you go to domain.com/about.php it removes .php and if you go to domain.com/about it simply remains like that.
Options +FollowSymlinks
RewriteEngine On
RewriteBase /
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.+)$ /$1.php [L,QSA]
RewriteRule ^(.*)/$ /$1 [L,R=301]
So, right now if you go to domain.com/about it displays the page, but if you go to domain.com/about.php it doesn't remove the extension.
Additionally, I have 301 redirects
redirect 301 /our-clients http://www.domain.com/about-ourclients
That works perfect, but if the user goes to domain.com/our-clients/ with the trailing slash, they are directed to about-ourclients.php
Any advice on how to rewrite my rules?

Answer 1

This should do the job:
Options +FollowSymlinks
RewriteEngine On
RewriteBase /
# remove .php ONLY if requested directly
RewriteCond %{THE_REQUEST} (\.php\sHTTP/1)
RewriteRule ^(.+)\.php$ /$1 [R=301,L,QSA]
# remove trailing slash ONLY if it is not an existing folder
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*)/$ /$1 [L,R=301]
# rewrite to FILENAME.php if such file does exist and is not a folder
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_FILENAME}\.php -f
RewriteRule ^(.*)$ /$1.php [L,QSA]
It will redirect all direct requests to php files: /something.php will be redirected to /something
Will remove the trailing slash IF requested resource is not directory. So if you requesting /home/ and you do have such folder, then it will NOT be redirected to /home.
Will internally rewrite requests to the same named PHP file IF it does exist. If you are requesting /about and you have /about.php then it will do rewrite; If you have no /about.php then nothing happens (well, at least not on these rules -- if you have more rules then such request can be matched later .. or 404 error page will be shown).
If you are requesting /about, you have /about.php and you also have /about folder, then request will go into folder. If you do not want this to happen ( /about should always be rewritten to /about.php) then you need to remove RewriteCond %{REQUEST_FILENAME} !-d from last block. But since you have exactly the same condition in your current .htaccess then I assume it is desired behaviour.