query_vars empty when using custom url with custom rewrite rule

Question

I'm trying to pass custom url parameters to pretty urls using

add_rewrite_tag('%product%', '([0-9/]+)');
add_rewrite_rule('^sign-up/product/([0-9/]+)?$','index.php?pagename=sign-up&product=$matches[2]','top');

and while I can go to /sign-up/product/60/ successfully

the $wp_query->query_var['product'] variable seems to be empty

I'm not sure what I am doing wrong...is there anything else I need to do again? I've flushed the rules several times just to be sure but no dice.

Answer 1

You only have one capture group, the ID is in matches[1], there is no matches[2].

EDIT-

Here is the working version I tested in the 2016 theme. I created a page with slug sign-up, added the following to functions.php, then visited the Permalinks Settings page to flush rewrite rules. The value passed to product is available in the template via get_query_var( 'product' );

function wpd_product_rewrite() {
    add_rewrite_tag( '%product%', '([0-9/]+)' );
    add_rewrite_rule(
        '^sign-up/product/([0-9/]+)?$',
        'index.php?pagename=sign-up&product=$matches[1]',
        'top'
    );
}
add_action( 'init', 'wpd_product_rewrite' );