To fix this issue, we had to add the “query variables” into the functions.php
of our theme to add them to the public variables.
function add_query_vars_filter($vars){
$vars[] = "subject";
$vars[] = "param";
return $vars;
}
add_filter('query_vars', 'add_query_vars_filter');
This allowed us to retrieve the variables’ value this way.
$subject = get_query_var('subject', false);