How to let htaccess distinguish between files and ids - .htaccess

Question

Options +FollowSymLinks
RewriteEngine On
RewriteCond %{HTTPS} !=on
RewriteRule ^ https://%{HTTP_HOST}%{REQUEST_URI} [L,R=301]
RewriteCond %{REQUEST_FILENAME} !-d # not an existing dir
RewriteCond %{REQUEST_FILENAME} !-f # not an existing file
RewriteCond %{DOCUMENT_ROOT}%{REQUEST_URI}\.php -f # and page.php exists
# redirect to the physical page
RewriteRule ^(.*)$ $1.php [L]
# otherwise, redirect to serve.php
RewriteRule ^ /serve.php [L]
RewriteRule ^(\w+)$ ./serve.php?id=$1
So in the first part of the code I just turn http into https. My aim is that I can use urls without an .php but in my old code I had the problem that if I did so, it was used as an id for my serve.php page. So if use https://example.com/contact it was like https://example.com/serve.php?id=contact but I want it to work as https://example.com/contact.php but on the other side I want that ids that arent directions or file should still work as ids. My old code was...
Options +FollowSymLinks
RewriteEngine On
RewriteCond %{HTTPS} !=on
RewriteRule ^ https://%{HTTP_HOST}%{REQUEST_URI} [L,R=301]
RewriteCond %{SCRIPT_FILENAME} !-d
RewriteCond %{SCRIPT_FILENAME} !-f
RewriteRule ^(\w+)$ ./serve.php?id=$1
RewriteEngine On
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^([^\.]+)$ $1.php [NC,L]

Answer 1

You can use these rules in your site root .htaccess:
Options +FollowSymLinks
RewriteEngine On
RewriteCond %{HTTPS} !=on
RewriteRule ^ https://%{HTTP_HOST}%{REQUEST_URI} [L,R=301,NE]
# skip rules below this for files and directories
RewriteCond %{REQUEST_FILENAME} -d [OR]
RewriteCond %{REQUEST_FILENAME} -f
RewriteRule ^ - [L]
# rewrite to the physical php page
RewriteCond %{REQUEST_FILENAME}.php -f
RewriteRule ^(.+?)/?$ $1.php [L]
# otherwise, redirect to serve.php
RewriteRule ^/?$ serve.php [L]
RewriteRule ^(\w+)/?$ serve.php?id=$1 [L,QSA]