.htaccess: adding trailing slash - php

Question

My entire .htaccess file consists of the following code:
Options +FollowSymLinks -MultiViews
rewriteEngine on
RewriteBase /
## Hide .php extension by external redirection:
RewriteCond %{THE_REQUEST} ^[A-Z]{3,}\s([^.]+)\.php [NC]
RewriteRule ^ %1 [R,NC]
## Internally redirect to .php extension:
RewriteCond %{REQUEST_FILENAME}.php -f
RewriteRule ^ %{REQUEST_URI}.php
## Redirect to index when page is missing.
ErrorDocument 404 http://www.domain.com
It (finally!) removes the *.php extension at the end. No complaints. But I've been struggling with inserting additional code to add a trailing slash (/). Nothing seems to work. Sometimes CSS is shut down and adding a slash after %1 results in errors.
In addition, I've read all kinds of stories online that using Multiviews and trailing slashes can create duplicate urls and other search engine problems. Maybe it's best to leave it as it is?
Can anybody give me some insight in the code to use here?

Answer 1

The trailing slash in the %1 is needed. The broken CSS is probably because you're using relative URL's in your content and the trailing slash changes the URI base. To fix that you need to either make all your links absolute URLs or add a base to your page header:
<base href="/" />
Then you'll need to change the internal rewrite that handles adding the php back, so something like:
Options +FollowSymLinks -MultiViews
RewriteEngine on
RewriteBase /
## Hide .php extension by external redirection:
RewriteCond %{THE_REQUEST} ^[A-Z]{3,}\s/+([^.]+)\.php [NC]
RewriteRule ^ /%1/ [R,NC,L]
## Internally redirect to .php extension:
RewriteCond %{DOCUMENT_ROOT}/$1.php -f
RewriteRule ^(.+?)/?$ /$1.php [L]
## Redirect to index when page is missing.
ErrorDocument 404 http://www.domain.com

Answer 2

It seems like a lot of code to remove .php for me it's enough using
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_FILENAME}\.php -f
RewriteRule ^(.*)$ $1.php
As for the Slash part it depends on your setup really.
but if you were to base your website from index.php
eg:
$key = $_GET["key"];
if($key = "about"){
include("about.php");
}
else if($key = "contact"){
include("contact.php");
}
else{
include("index.php");
}
and use the following code in .htacces
#RewriteRule ^([a-zA-Z0-9_-]+)$ index.php?key=$1
#RewriteRule ^([a-zA-Z0-9_-]+)/$ index.php?key=$1
Works for me! :)