submitting a GET form with query string params and hidden params disappear

Question

Consider this form:

Answer 1

If you need workaround, as this form can be placed in 3rd party systems, you can use Apache mod_rewrite like this:

RewriteRule ^dummy.link$ index.php?a=1&b=2 [QSA,L]

then your new form will look like this:

and Apache will append 3rd parameter to query