htaccess rewriting rule does not work for homepage - php

Question

I have a PHP website. I want to convert the PHP page names into SEO friendly page names.
So, first of all I want to convert the homepage, I want to remove the mention of "index". As its a multilanguage site, there are english and french versions of the homepage.
I want:
www.abc.com/index.php?lang=fr
to become
www.abc.com/fr/
However, after that, I want other pages to keep their name, for example:
I want:
www.abc.com/links.php?lang=fr
to become
www.abc.com/fr/links/
I also want the url to work without the trailing slash.
So this:
www.abc.com/fr/links
should give the same page as this:
www.abc.com/fr/links/
and this:
www.abc.com/fr
should give the same page as this:
www.abc.com/fr/
The contents of my htaccess file so far is below.
It enables me to change the links page correctly, however, I can't figure out how to do the index page in the way I describe above (plus it is possible that the code below is very bad, as I am only a starter on htaccess so don't hold back on the criticism, I'm mainly advancing by guesswork so far...)
RewriteEngine On
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.+)/index(/*)$ index.php?lang=$1 [L]
RewriteRule ^(.+)/links(/*)$ links.php?lang=$1 [L]

Answer 1

I would match allowed languages explicitly to have more control about what URLs are matched.
If you had "fr" and "en" allowed, it should work with the following:
RewriteEngine On
# Rewrite /fr/links and /fr/links/ to links.php?lang=fr
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(en|fr)/(.+)(/?)$ $2.php?lang=$1 [L]
# Rewrite /fr and /fr/ to index.php?lang=fr
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(en|fr)(/?)$ index.php?lang=$1 [L]
While this should work, I would rather go a different route in the actual implementation. I would redirect all requests to a single index.php file and do the route matching there, which keeps your .htaccess clean and simple:
RewriteEngine On
# Rewrite everything not existing to index.php
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule .* index.php [L]
And in index.php parse language and page and do your includes appropriately.