.htaccess, redirect a whole folder (on the root directory) to subdomain

Question

Current state

Redirect 301 "/myFolder" "http://mySubdomain.site.com/"

Expected result

- site.com/myFolder
- site.com/myFolder/
- site.com/myFolder/index.php 
- site.com/myFolder/blabla/
- site.com/myFolder/blabla/blablablaaa

-> mySubdomain/site.com

Current results

- site.com/myFolder -> mySubdomain/site.com [OK]
- site.com/myFolder/ -> mySubdomain/site.com [OK]
- site.com/myFolder/index.php -> mySubdomain/site.comindex.php [NOT CORRECT]
- site.com/myFolder/blabla/ -> [ERROR 404]
- site.com/myFolder/blabla/blablablaaa -> mySubdomain/site.com

Answer 1

Use the rewriting module instead:

RewriteEngine on
RewriteRule ^/?myFolder(?:$|/(.*)$) https://sub.example.com/$1 [R=301]

It is a good idea to start out with a 302 temporary redirection and only change that to a 301 permanent redirection later, once you are certain everything is correctly set up. That prevents caching issues while trying things out...

This implementation will work likewise in the http servers host configuration or inside a dynamic configuration file (".htaccess" file). Obviously the rewriting module needs to be loaded inside the http server and enabled in the http host. In case you use a dynamic configuration file you need to take care that it's interpretation is enabled at all in the host configuration and that it is located in the host's DOCUMENT_ROOT folder.

And a general remark: you should always prefer to place such rules in the http servers host configuration instead of using dynamic configuration files (".htaccess"). Those dynamic configuration files add complexity, are often a cause of unexpected behavior, hard to debug and they really slow down the http server. They are only provided as a last option for situations where you do not have access to the real http servers host configuration (read: really cheap service providers) or for applications insisting on writing their own rules (which is an obvious security nightmare).