Strange behavior with URL rewriting - apache

Question

I'm trying to rewrite some url's. So I have page which is userAction.php and I rewrite it to /login/ like this
RewriteRule ^login/$ /userAction.php [L]
now on that page login I have two forms - Login and Register. When user make registration and he finish with it the page is still userAction.php but with message: userAction.php?action=joined. I want to rewrite this to login?action=joined. Here is what I'm tried but it it redirecting me to 404 error
RewriteRule ^login?action=joined/$ /fun-second/userAction.php?action=joined [L]
So this is the whole .htaccess
RewriteRule ^login/$ /userAction.php [L]
RewriteRule ^login/?action=joined/$ /userAction.php?action=joined [L]
And this is the redirect when registration is successfully
header('Location: login/?action=joined/');
exit;
Note: With normal URL's is working and there is no problems.

Answer 1

You'd use %{QUERY_STRING} variable to match it.
RewriteEngine On
RewriteCond %{QUERY_STRING} ^(action=joined)$ [NC]
RewriteRule ^login/$ /userAction.php?%1 [NC,L]
RewriteRule ^login/$ /userAction.php [NC,L]
The order of rules is also important. Alternatively, you can try the following approach:
RewriteEngine On
RewriteRule ^login/$ /userAction.php [QSA,NC,L]
Note the QSA flag above.