Is it possible to mod_rewrite BASED on the existence of a file/directory and uniqueID?

Question

My site currently forces all non-www. pages to use www.

Ultimately, I am able to handle all unique subdomains and parse correctly but I am trying to achieve the following (ideally with mod_rewrite):

When a consumer visits www.example.com/john4, the server processes that request as:
www.example.com?Agent=john4

Our requirements are:

• The URL should continue to show www.example.com/john4 even though it was redirected to www.example.com/index.php?Agent=john4

• If a file (of any extension OR a directory) exists with the name, the entire process stops an it tries to pull that file instead:

  For example: www.example.com/file would pull up (www.example.com/file.php if file.php existed on the server. www.example.com/pages would go to www.example.com/pages/index.php if the pages directory exists).

Answer 1

If you turn on MultiViews, you can do this, as it will search for request-uri.* first before running the RewriteRule.

Options +MultiViews
RewriteEngine On
RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^([^/]+)/?$ index.php?Agent=$1 [L]

Answer 2

Try this (untested)

<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^([^/]+)/?$ index.php?Agent=$1 [L]
</IfModule>