.htaccess URL rewriting with end-slash

[X96 Web Design]

I have the following in my .htaccess file, and it removes the .php of the URL for 'friendly urls'.

	RewriteEngine on
	RewriteCond %{REQUEST_URI} !(\.[^./]+)$
	RewriteCond %{REQUEST_fileNAME} !-d
	RewriteCond %{REQUEST_fileNAME} !-f
	RewriteRule (.*) /$1.php [L]
	RewriteCond %{THE_REQUEST} ^[A-Z]{3,9}\ /([^.]+\.)+php\ HTTP
	RewriteRule ^(.+)\.php$ /$1 [R=301,L]

How do I modify it so that it puts a slash at the end?

Here's an example:
Original: /about.php
Rewritten: /about/

Thanks for you help!

// X96 \\