Using .htaccess to redirect all requests from subdomain to main domain - .htaccess

Question

I have a hobby website for a number of different projects and want each project to have it's own subdomain, like foo.domain.com, bar.domain.com etc.
I use Drupal with the Domain Access module, meaning all subdomains should point to the base installation of Drupal, and then the module recognizes what subdomain the request comes from and serves a page according to that.
Now, since this is just a hobby project, I keep it on a free shared hosting account, which means a few limitations:
No wildcard subdomains.
Each subdomain is linked to a subdirectory with the same name, for example domain.com goes to /public_html/ and sub.domain.com goes to /public_html/sub/ The hosting forces this.
I can't create symlinks.
I have limited space and databases, meaning I can't just make a new installation for each project. (Hence the Domain access module)
My domain registrar (Godaddy) doesn't play nice with shared hosting. I tried hosting the DNS with them and doing a wildcard A record to my hosting server, but it didn't work, and Godaddy don't allow wildcard CNAME records for some reason...
It seems the only option left for me is some .htaccess magic.
I need a .htaccess file to put in the subdomain director(y/ies) to tell apache:
The data is in the root web directory
To not change anything else, so that the Drupal module knows what subdomain was requested and the user still sees "sub.domain.com" in the browser window.
Thankful for your help!
TL;DR
How can I tell Apache to use the data from another directory (i.e. /public_html/ instead of /public_html/subdomain/) WITHOUT making a redirect or any changes to the headers? HTTP_HOST needs to be intact.
Thanks!

Answer 1

Try this:
http://kb.mediatemple.net/questions/242/How+do+I+redirect+my+site+using+a+.htaccess+file%3F

Answer 2

try this
RewriteEngine On
RewriteCond %{HTTP_HOST} !^example\.com$ [NC]
RewriteRule ^(.*)$ http://example.com%{REQUEST_URI} [R=301,L]

Answer 3

try this.
RewriteEngine On
RewriteCond %{HTTP_HOST} sub\.example\.com$ [NC]
RewriteRule ^sub/(.*)$ $1 [L]
Not sure if it will work, because I don't know how your host configured to server to map the subdomains to a different folder.
Otherwise you could try the Proxy flag, but that will not set the correct http_host variable in php.
Are you sure Drupal doesn't have a different method of doing multiple installs. I know WP did have a option to use a prefix for all table-names so multiple installs can coexist, using the same database, as long as they use different prefixes. Not sure how big a Drupal install is, and what amount of diskspace your host provides.