apache redirect / Rewrite-Engine - apache

Question

Is the following possible?
A user requests the url http://example1.com/example.php and the apache opens http:// example1.com/example.php?id=1
A user requests the url http://example2.com/example.php and the apache opens http:// example2.com/example.php?id=2
But the user should not see the id in his browser adress bar (the user should only see http://example1.com/example.php or http://example2.com/example.php).
You can say the id is invisible for the user but transfered to the example.php.
How can I implement this?

Answer 1

Is that the correct solution?
RewriteEngine On
RewriteRule ^/example.php http://example1.com/example.php$1 [P]
ProxyPassReverse /example.php?id=1 http:// example1.com/example.php
RewriteEngine On
RewriteRule ^/example.php http://example2.com/example.php$1 [P]
ProxyPassReverse /example.php?id=2 http:// example2.com/example.php

Answer 2

You have to understand several concept.
Once the server received the user requested url he can do several things
Take the requested path from the url and use it without modifications. That's the default solution
Map the requested path to any other physical path, things that can be done via Alias, AliasMatch or RewriteRules.
Map the requested path to another website while hiding the fact thtat another website is requested. That's the proxy solution, thta mod_proxy or mod_rewrite could handle (but you do not need that)
Redirect the user to another path, sending him a new url to use, making another client/server roundtrip, with Redirect instructions or mod_rewrite (the swiss knife). But you do no need that.
So you want a server-side only remapping of the requested path.
Let,s say we will use mod rewrite to make this mapping. If you check all tags available in RewriteRule (summary here) the interesting ones are:
passthrough|PT : Forces the resulting URI to be passed back to the URL mapping engine for processing of other URI-to-filename translators, such as Alias or Redirect.
qsappend|QSA: Appends any query string from the original request URL to any query string created in the rewrite target
last|L: Stop the rewriting process immediately and don't apply any more rules. Especially note caveats for per-directory and .htaccess context (see also the END flag)
nocase|NC: Makes the pattern comparison case-insensitive.
details on the PT flag shows that:
The target (or substitution string) in a RewriteRule is assumed to be a file path, by default.
Well, that,s maybe enough for you. But using PT is a good thing, if you have other apache configusation elements you should try to let them apply after mod_rewrite job.
So... assuming you may need to handle some query strings arguments and that this id argument is based on the domain name in the request, and that only the example.php script needs this behavior; you should start your research with such rules (untested):
RewriteEngine On
RewriteCond %{HTTP_HOST} ^example1.com$ [nocase]
RewriteRule ^example\.php$ example.php?id=1 [passthrough,qsappend,last]
RewriteCond %{HTTP_HOST} ^example2.com$ [nocase]
RewriteRule ^example\.php$ example.php?id=2 [passthrough,qsappend,last]