How do I redirect subdomain to subdirectory (with default folder) on htaccess without change address

Question

I'm trying to do a Rewrite subdomains to subdirectories on htaccess. Searching here I did the rule below:

RewriteEngine On
RewriteCond %{HTTP_HOST} !^(www)\. [NC]
RewriteCond %{HTTP_HOST} ^(.+)\.domain\.com\.br
RewriteCond %{REQUEST_URI} !^/sd_
RewriteRule ^(.*)$ http://domain.com.br/sd_%1/$1 [P,L,NC,QSA]

RewriteEngine On
RewriteCond %{HTTP_HOST} ^www.(.*)\.domain\.com\.br
RewriteCond %{REQUEST_URI} !^/sd_
RewriteRule ^(.*)$ http://domain.com.br/sd_%1/$1 [P,L,NC,QSA]

#Rewrite for my Framework
RewriteEngine On
RewriteCond %{SCRIPT_FILENAME} !-f
RewriteCond %{SCRIPT_FILENAME} !-d
RewriteRule ^(.*)$ index.php?url=$1

When I access the address: http://user.domain.com.br or the address: http://www.user.domain.com.br they're redirected without change the URL address to: http://www.domain.com.br/sd_user/

Well, fine. My problem is:
When someone access a adrees with haven't a folder, .htaccess redirect it to a specific folder. For example:
I haven't a folder called "sd_joecompany", then I want to redirect it to a default folder named "sd_system". If I access http://joecompany.domain.com.br/ and not exists the respective folder, this address may point to "sd_system" keeping the address.

With this code, when I access a subdomain without a respective folder, the following error appear:

Proxy Error

The proxy server received an invalid response from an upstream server. The proxy server could not handle the request GET /index.php.

Reason: Max-Forwards has reached zero - proxy loop?

I'm not sure about the clarity of my doubt, and I'm sorry for my poor english. I know a little about .htaccess and these rules. Everithing on the code above, I gathered here!

Thank you since now!

Answer 1

If they are on the same server and have the same document root, then you really don't want to proxy at all. Remove the host part of the rule and get rid of the "P":

RewriteEngine On

RewriteCond %{REQUEST_URI} !^/sd_
RewriteCond %{HTTP_HOST} !^(www)\. [NC]
RewriteCond %{HTTP_HOST} ^([^.]+)\.domain\.com\.br$ [NC]
RewriteCond %{DOCUMENT_ROOT}/sd_%1%{REQUEST_URI} -f [OR]
RewriteCond %{DOCUMENT_ROOT}/sd_%1%{REQUEST_URI} -d
RewriteRule ^(.*)$ /sd_%1/$1 [L,NC,QSA]

RewriteCond %{REQUEST_URI} !^/sd_
RewriteCond %{HTTP_HOST} ^www\.([^.]+)\.domain\.com\.br$ [NC]
RewriteCond %{DOCUMENT_ROOT}/sd_%1%{REQUEST_URI} -f [OR]
RewriteCond %{DOCUMENT_ROOT}/sd_%1%{REQUEST_URI} -d
RewriteRule ^(.*)$ /sd_%1/$1 [L,NC,QSA]

#Rewrite for my Framework
RewriteCond %{SCRIPT_FILENAME} !-f
RewriteCond %{SCRIPT_FILENAME} !-d
RewriteRule ^(.*)$ index.php?url=$1

Cleaned up some of the regex and got rid of the extra RewriteEngine On's.