.htaccess rewrite cond and rule cannot firgure out extra slash at end - apache

Question

I've been googling around stack overflow trying to figure this out but have had no joy and keep getting errors no matter what I try.
i am currently using this code to rewrite the address to remove extensions, I got it from a SO post a while ago for simple websites:
RewriteEngine on
# To externally redirect /dir/foo.html to /dir/foo
RewriteCond %{THE_REQUEST} ^[A-Z]{3,}\s([^.]+)\.html [NC]
RewriteRule ^ %1 [R=301,L]
# To internally forward /dir/foo to /dir/foo.html
RewriteCond %{REQUEST_FILENAME}.html -f
RewriteRule ^ %{REQUEST_URI}.html [L]
# To externally redirect /dir/foo.html to /dir/foo
RewriteCond %{THE_REQUEST} ^[A-Z]{3,}\s([^.]+)\.phtml [NC]
RewriteRule ^ %1 [R=301,L]
# To internally forward /dir/foo to /dir/foo.html
RewriteCond %{REQUEST_FILENAME}.phtml -f
RewriteRule ^ %{REQUEST_URI}.phtml [L]
(i use phtml files as ui files and php for background files, hence the second block)
This works fine for me but now i am on a site where i would like to feed get variables to a page for bookmarking etc and do not want the address to be some thing like www.website.com/page?var=0
i have managed to get my testing site to load www.website.com/page/ using code from another SO post, but only if i enter that url, it will not rewrite if i go to page.html and will not load the attached files css, js (i understand this is because the files have a relative path) Edit: I now understand this is to do with -f || !-f;
code:
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_FILENAME}\.html -f
RewriteRule ^([^/]+)/$ $1.html
RewriteRule ^([^/]+)/([^/]+)/$ /$1/$2.html
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_URI} !(\.[a-zA-Z0-9]{1,5}|/)$
RewriteRule (.*)$ /$1/ [R=301,L]
I am fine with either having or not having a trailing slash, but I do want to add it when there are variables, like page?var=0 to page/var=0 without the images, js and css stopping. of course if it can all be with a slash then all the better.
Thanks
Edit: Also needs to work when the website and .htaccess are in a subfolder, like: mysite.com/example/websitedemonstration/page

Answer 1

This one seems to work fine for me, give it a try:
Options +FollowSymLinks -MultiViews
RewriteEngine On
RewriteBase /
# To externally redirect /dir/foo.html to /dir/foo
RewriteCond %{THE_REQUEST} ^[A-Z]{3,}\s([^.]+)\.(html|phtml) [NC]
RewriteRule ^ %1 [R=301,L]
# To internally forward /dir/foo to /dir/foo.html
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_FILENAME}\.html -f
RewriteRule ^([^/]*)/?$ $1.html [L]
# To internally forward /dir/foo to /dir/foo.phtml
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_FILENAME}\.phtml -f
RewriteRule ^([^/]*)/?$ $1.phtml [L]