Redirect page on subdomain only when no URL query string is present

Question

Pretty specific htaccess question: I have a page at http://subdomain.example.com/page/ that contains a form. The page should only be accessed with auto-created links that contain query strings that feed information through the form. What I need is an htaccess rule that will redirect traffic coming to this page to my homepage at http://example.com/ whenever it is reached without a query string in the URL.

Put another way: if someone reaches http://subdomain.example.com/page/ they need to redirect to http://example.com . But if someone reaches http://subdomain.example.com/page/?querystring they need to stay on the page.

How do i solve this with htaccess?

Answer 1

try:

RewriteEngine On
RewriteCond %{HTTP_HOST} ^subdomain\.example\.com$ [NC]
RewriteCond %{QUERY_STRING} ^$
RewriteRule ^page/ http://example.com/ [L,R]

or

RewriteEngine On
RewriteCond %{HTTP_HOST} ^subdomain\.example\.com$ [NC]
RewriteCond %{THE_REQUEST} !\?
RewriteRule ^page/ http://example.com/ [L,R]