RewriteEngine On
# The following rule tells Apache that if the requested filename
# exists, simply serve it.
RewriteCond %{REQUEST_FILENAME} -s [OR]
RewriteCond %{REQUEST_FILENAME} -l [OR]
RewriteCond %{REQUEST_FILENAME} -d
RewriteRule ^.*$ - [NC,L]
# The following rewrites all other queries to index.php. The 
# condition ensures that if you are using Apache aliases to do
# mass virtual hosting, the base path will be prepended to 
# allow proper resolution of the index.php file; it will work
# in non-aliased environments as well, providing a safe, one-size 
# fits all solution.
RewriteCond %{REQUEST_URI}::$1 ^(/.+)(.+)::\2$
RewriteRule ^(.*) - [E=BASE:%1]
RewriteRule ^(.*)$ %{ENV:BASE}index.php [NC,L]