mod_rewrite? question - tricky case

I have a PHP script, redirector.php on Server A that redirects requests to Server B. For instance a file is requested on Server A via the url: http://servera.com/redirector.php?filename=test.txt

redirector.php send the request to server be like so:

header("Location: http://serverb.com/test.txt");

Code (markup):

.

It's important that requests to Server B arrive via the redirect from Server A. If they don't, I'd like to use a ReWriteRule or RewriteCond? to rewrite the requests back to Server A: http://servera.com/redirector.php?filename=test.txt

Does anyone know if this is possible? Can any of the HTTP headers tell you if a visitor arrived via a redirect (or even a url rewrite)?

Thanks in advance-

m

 

Sorry its late but I think using the referal url you can do what you are doing.

 

The headers won't be able to tell you whether the visitor came from a redirect or not, but the HTTP_REFERRER variable will tell you which URL they came from, so you can use that in a RewriteCond