In the .htaccess for this directory, there are the following rules:
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^mod_rewrite_substring http://google.com [R,L]
If a file doesn't exist and it begins with mod_rewrite_substring, then redirect to Google. This works as you would expect with mod_rewrite_substring.dne. It forwards to Google. With mod_rewrite_substring.test however, it opens this page, mod_rewrite_substring.test.php, even though the file extension is missing.
I have a project where I am trying to forward URLs where a file with a name that is a superstring exists and this behavior is keeping that from working.
It only does this on my server at home, a Fedora Core box running stock Apache 2.2.3. Under OSX it works as expected, as does it on Dreamhost.
This machine is running: Apache.
If you think you know the solution and would like to test a solution, you can download this script. I'm pretty sure it is a Fedora bug and I've filed a report since the behavior doesn't exist on any other distributions I have access to.