how do I add custom variable?

trying to get this to work

I need to be able to pass a custom variable to all the links as the visitor moves through the site ?rid=”a user id”

That way you can share your link wordpresssite.com/?rid=2 and people check it out and want to join you can give them a signup link with member.wordpresssite.com/?rid=2

I added 2 functions to the function.php

`function add_query_vars_filter( $vars ){
$vars[] = “rid”;
return $vars;
}
add_filter( ‘query_vars’, ‘add_query_vars_filter’ );`

and

`function pass_rid () {
if( !is_admin() && isset($_GET[‘rid’]) )
{
$rid = $_GET[‘rid’];
$location = “http://”.$_SERVER[‘SERVER_NAME’].$_SERVER[‘REQUEST_URI’];
$location .= “?rid=”.$rid;

echo $location;
wp_redirect( $location );

}
}
add_action(‘template_redirect’, ‘pass_rid’);`

I end up with endless loops

The echo is just to see if it is grabbing the variable