.htaccess: Want query string added to 301 Redirect to same url

Question

Example: When someone visits this URL

http://example.com/site/register

I'd like this query string to be automatically added:

http://example.com/site/register?destination=thankyou

I've tried the following in my .htaccess file:

Redirect 301 /site/register /site/register?destination=thankyou

But this creates an infinite redirect loop.

I've crawled the web for hours for a solution but to no avail. Thanks in advance.

Answer 1

if register is PHP, use something like:

<?php
  if(!array_key_exists('destination',$_GET))
    header('Location: '.http_build_query(
        array_merge($_GET,array('destination'=>'thankyou')));