Rewrite weird difference between servers - regex

Question

Today I wrote the following rewrite rules:
RewriteCond %{HTTP_HOST} ^visionale\.book [NC]
RewriteRule ^\/([^/]+)\/$ $1.php [L]
RewriteCond %{HTTP_HOST} ^(www\.)?visionale\.se [NC]
RewriteRule ^(.*)/$ $1.php
The firs is for my laptop where I run Apache, the second rule for the web hotel.
Applying the first rewrite on the web hotel results in a 404 Not Found
Applying the second rule on my laptop mysteriously results in "pagename.php.php.php" not found.
Now the solution I provided works at both locations but I am baffled about what really is happening. My local machine runs Apache 2.4.6. The web hotel runs Litespeed. So this is an incompatibility of course, but exactly how.
My guess is that Litespeed misses the first rule because of missing functionality, but why does Apache not get the easier one, that I've used many times in the past?
Edit: Clarifying the questions.
This rule:
RewriteRule ^\/([^/]+)\/$ $1.php [L]
Is not picked on my web hotel running Litespeed. My guess is that this is because Litespeed has a flawed rewrite implementation. I'd like to get that hunch confirmed or another explanation privided.
This rule:
RewriteRule ^(.*)/$ $1.php
Does not work on my dev-machine any more but it has worked in the past. It seems simple enough. Anything ending with a trailing slash should instead get a ".php" extension. However, on my dev machine it adds three ".php" instead of one. The rule works as intended in the web hotel and it has worked for me locally in the past. This is puzzling and I would like an explanation.

Answer 1

Both rules are incorrect. Let me provide you correct code first:
Options +FollowSymLinks -MultiViews
# Turn mod_rewrite on
RewriteEngine On
RewriteBase /
RewriteCond %{HTTP_HOST} ^visionale\.book$ [NC]
# If the request is not for a valid file
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^([^/]+)/?$ $1.php [L]
RewriteCond %{HTTP_HOST} ^(www\.)?visionale\.se$ [NC]
# If the request is not for a valid file
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^(.+?)/?$ $1.php [L]
Now the problems in your code:
RewriteRule in .htaccess doesn't start matching with leading slash which is striped by mod_rewrite
You need to avoid rematching these rules using RewriteCond %{REQUEST_FILENAME} !-f otherwise mod_rewrite will keep adding .php in the URI.