Hide a folder from the URI with RewriteRule in a .htaccess file

Question

I would really appreciate if you could help me building my .htaccess file.
What I want to achieve here is moving all of my domain's files and folders to a root subfolder ("mydomain") and make sure that the URL visible to my visitors still looks like

domain.com/file.extention  

instead of

domain.com/mydomain/file.extention 

or

domain.com/subfolder/file.extention

instead of

domain.com/mydomain/subfolder/file.extention

This is my folders tree:

/
  /mydomain
    /subfolder
    index.php
    test.php

and here is my current .htaccess file:

<IfModule mod_rewrite.c>

# System symbolic links are allowed.
Options +FollowSymlinks

# Runtime rewriting engine enabled.
RewriteEngine On

#
# BEGIN DOMAIN
#

# Make 'mydomain' subfolder the root folder for the domain.
RewriteCond %{HTTP_HOST} ^((www\.)?domain\.com) [NC]
RewriteRule ^\/?$ mydomain/ [NC,L,S=1]

RewriteCond %{HTTP_HOST} ^(www\.)?domain\.com$ [NC]
RewriteCond %{REQUEST_URI} !^/?mydomain/ [NC]
RewriteCond %{REQUEST_FILENAME} !-f 
RewriteCond %{REQUEST_FILENAME} !-d 
RewriteRule ^(.+)$ mydomain/$1 [NC,L]

#
# END DOMAIN
#

</IfModule>

The problem here is that it works when I browse for

domain.com/subfolder/

but not with

domain.com/subfolder

and with

domain.com/index.php

but not with

domain.com/test.php

Thank you all,
Matteo

Answer 1

Changing domain.com/mydomain/file.extention to domain.com/file.extention

use this for example

RewriteRule ^mydomain/(.+)$ http://www.domain.com/ [R=301,L]

But if you redirects working just for some pages check that you clear browser cache or use another one instead