I am using ModRewrite as below to convert urls on my site to be SEO friendly:
RewriteRule user/(.*)/$ seo-url-user-by-name.php?username=$1
Now I am writing code for seo-url-user-by-name.php and am looking for a way in PHP to redirect to:
user.php?uid=<uid>
so that seo-url-user-by-name.php will essentially return the contents of user.php?uid=<uid> BUT without changing the address in address bar to user.php?uid=<uid>
How do I do that?
Simply include user.php in seo-url-user-by-name.php. To get the querystring right you have to overwrite the value in $_GET.
$_GET['uid'] = 'whatever you want';
include 'user.php';
You're going about it backwards. The only URLs your code should be outputting are the 'friendly' ones. Those are the urls that will appear in the produced HTML and what will show up in the user's address bar.
e.g.
<a href="/user.php?id=foo">Bad URL</a> (URL #1)
<a href="/user/foo">This URL is fine</a> (URL #2)
You should never output anything but URL #2's. It'll be your server's responsibility to convert that clean (and in real terms, non-existent) URL to whatever really is on the server. PHP itself should never care nor see the /user/foo URL. PHP will be invoked as /user.php?id=foo as usual, and go about its business as usual.
The remote user would never see that rewriting occurring, they'll just see a request go out for /user/foo.