.htaccess - Redirect all to index.php for root folder or subfolder - apache

Question

I need an .htaccess file that will work whether it is put in the root folder or a subfolder without modification. The script below is the normal one that I've been trying to adapt without success. I tried the solution on htaccess rewrite index.php on root and subfolders and couldn't get it to work.
<IfModule mod_rewrite.c>
RewriteEngine on
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*)$ index.php/$1 [L]
</IfModule>
Layout
.htaccess
index.php
subfolder1
- .htaccess
- index.php
The route /blah should go to /index.php and /subfolder1/whatever should go to /subfolder1/index.php. Currently, the above script will send /subfolder1/whatever to /index.php.
[Update]
This should also work for any path under subfolder1, like /subfolder1/1/2/3/idunno.

Answer 1

If you are using Apache 2.2.16 and later, you can just stop using mod_rewrite, which although extremely useful and powerful, can get messy as hell.
A new directive in mod_dir was introduced, FallbackResource which does just that, redirecting to the uri of your choice if there is no hit on the file system. It is available in .htaccess files as long as AllowOverride Indexes is specified for the directories in the configuration.
As .htaccess files are evaluated depth-first, you just have to have each .htaccess file describe your fallback resource in the current directory, and the one in the subdirectory subfolder1 will take precedence:
subfolder1/.htaccess:
FallbackResource index.php
.htaccess:
FallbackResource index.php
They're both the same, and work just right.
It seems this directive is not well known yet even though it's been around for a few years, and its goal is precisely to solve that problem in an elegant way.
There is only one limitation with that setup. Calling urls in non-existing sub-directories of the root dir or subfolder1 will yield subrequest recursion and subsequently an error 500, because the fallback resource is local to the given directory.
The best approach is to have absolute uris (beginning with '/') as parameter to FallbackResource, which is why it is true that the requirement in itself is kind of odd, and is probably not playing too well with the inner workings of Apache.