Enpoint Not Found in Rewrite Tag Permalink

Question

I'm trying to make an XML feed show nice and pretty permalinks rather than showing query strings. The problem is I can't get my /products/ endpoint to show up when trying to process my custom rewrite template tag. Here's what I have:

/** Register Query Vars **/
function theme_custom_query_vars( $vars ){
    $vars[] = 'custom_category';
    $vars[] = 'products';
    return $vars;
}
add_filter( 'query_vars', 'theme_custom_query_vars' );

/** Register Endpoint **/
function theme_register_endpoints() {
    add_rewrite_rule( '^products/?', 'index.php?products=products', 'top' );
    add_rewrite_rule( '^products/([^/])/?', 'index.php?products=products&custom_category=$matches[2]', 'top' );

    add_rewrite_tag( '%custom_category%', '([0-9])' );
}
add_action( 'init', 'theme_register_endpoints' );

That's fine - my products endpoint exists and I can redirect it to a specific template. Now the issue is that while wp_query knows that custom_category exists and has a value assigned to it, the passed $permalink only shows my base URL ( http://domain.com/ ) so I cannot replace the template tag since it doesn't exist in my $permalink variable.

/** Process our Rewrite Tag **/
function theme_rewrite_tags_filter( $permalink ) {
    global $wp_query;
    printf( '<pre>%s</pre>', print_r( $wp_query, 1 ) );
    die( $permalink );

    if( false !== strpos( $permalink, '%custom_category%' ) ) {
        die( 'made it!' );
    }

    return $permalink;
}
add_filter( 'page_link', 'theme_rewrite_tags_filter' );

I gotta be missing something in regards to template tags or maybe I have a misunderstanding of how endpoints are structured but the $permalink just isn't showing the products endpoint or the %custom_category% template tag:

• http://domain.com/products/ ( works! )
• http://domain.com/?products=products ( works! )
• http://domain.com/products/?custom_category=2 ( doesn't work... )

---

The Situation

I'm working with an external API that gives me an XML feed of items and categories. The API works with category IDs and returns items in that category. What I'm trying to do is the following:

• Make an endpoint products which shows all the available categories: domain.com/products/
• Make a dynamic endpoint that passes the category ID via query string ?custom_category=2 and rewrites it into a pretty permalink like domain.com/products/categoryname/ - I don't know the category names so I need to ask the API the category name by the given ID.
• Finally, in a similar fashion as above I need to take a given item ID via query string item_id=17 and rewrite it into a pretty permalink of which I'm not picky: domain.com/products/productname/ or domain.com/products/categoryname/productname/ - I don't know the item names so I need to ask the API the item name by the given ID.

I have to use IDs in links because the API is old and doesn't understand slugs ( so I can't pass my API a slug and expect results I need to pass an ID of some kind ) but I was hoping to grab the ID from the query string, hit the API to get the name, make it URL friendly and put it into the URL.

Answer 1

Rewrite tags aren't used in the context of add_rewrite_rule. If you were to use your tag in the post permalink settings under Settings > Permalinks, then your tag would be present in the link passed to the post_link filter. I think you need to add a new permalink structure containing the tag directly to the rewrite object to have a custom tag in there. As it stands, it's redundant since you're already adding query vars (which add_rewrite_tag also does). Also note that in your 2nd rule, the value of custom_category is in $matches[1]. For your page_link filter, you can use the 2nd argument passed to the filter, which is the page object, to check if that page has a custom_category and build the permalink you need in that case.