Force SSL HTTPS for subdomain with .htaccess - php

Question

I have this code for forcing SSL on a website generally:
RewriteCond %{HTTPS} !=on
RewriteRule ^ https://%{HTTP_HOST}%{REQUEST_URI} [L,R=301]
Which I got from here
I would like it to only apply to a specific sub-domain.
For example, if you were to visit http://sub.domain.org it should redirect to https://sub.domain.org.
I have a hunch that I need to add another RewriteCond which basically says is the domain that is being hit is http://sub.domain.org, but I am at a loss on how to write this code.
I've been looking at other stackoverflow questions such as:
Force HTTPS and WWW for domain and only HTTPS for subdomains HTACESS
Force SSL/https using .htaccess and mod_rewrite
and the Apache docs: https://httpd.apache.org/docs/current/mod/mod_rewrite.html#rewritecond
And I've had these attempts:
RewriteCond %{HTTPS} !=on
RewriteCond %{HTTP_HOST} !^(reports\.)?uksacb\.org$ [NC]
RewriteRule ^.*$ https://%1%{REQUEST_URI} [R,L]
Sort of reversed the answer in this question/answer:
RewriteCond %{HTTPS} !=on
RewriteCond %{HTTP_HOST} =reports.uksacb.org
RewriteRule ^ https://%{HTTP_HOST}%{REQUEST_URI} [L,R=301]
However I'm still failing to make sense of how to do it correctly.
If anyone could explain to me what I'm doing wrong, what I need to do to get it right and how does one go about debugging their rewrite conditions and rules to make sure it works properly I'd be very grateful. Sometimes I think my browser is caching the rules I've written and my different attempts are not taking any affect!
My whole .htaccess looks like this:
Options -MultiViews
RewriteEngine On
# Redirect Trailing Slashes If Not A Folder...
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*)/$ /$1 [L,R=301]
# Force SSL
RewriteCond %{HTTPS} !=on
RewriteRule ^ https://%{HTTP_HOST}%{REQUEST_URI} [L,R=301]
# Handle Front Controller...
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^ index.php [L]

Answer 1

To avoid using the domain or subdomain names I used to use the following code:
# Redirect HTTP to HTTPS
RewriteCond %{HTTPS} off
RewriteCond %{HTTP:X-Forwarded-Proto} !https
RewriteRule ^(.*)$ https://%{HTTP_HOST}%{REQUEST_URI} [L,R=301]
I prefer without WWW.
%{HTTPS} Set to on if the request is served over SSL.
%{HTTP_HOST} Everything between the protocol (http:// or https://) and the request (/example-file.txt).
%{REQUEST_URI} Everything after the server address — for example, a request to http://example.com/my/example-file.txt sets this value as my/example-file.txt.
%{HTTP:X-Forwarded-Proto} The protocol used when the URL was requested — set to http or https.
I hope it can be useful for anybody.

Answer 2

For debugging I use a website I found https://htaccess.madewithlove.be/
Using the rules you provided
RewriteCond %{HTTPS} !=on
RewriteRule ^ https://%{HTTP_HOST}%{REQUEST_URI} [L,R=301]
I got an error at
RewriteCond %{HTTPS} !=on
This might work for you
RewriteCond %{HTTPS} off
RewriteRule (.*) https://%{SERVER_NAME}/%$1 [R,L]
Found the above example at https://www.sslshopper.com/apache-redirect-http-to-https.html