Is there a way to add custom endpoint to specific page only

Question

Hope everyone is fine, I am learning custom endpoints in WordPress. I know how to create endpoints and how they work(a little bit). But I got stuck when I wanted to add an endpoint to only one page. Let me give you an example of what I want to do.

1. A page named as example having id 77.
2. Set a custom template to it like some-template.php
3. If the user has set this template create endpoints like example.com/example/endpoint1 or example.com/example/endpoint2
4. if the user opens another page like example.com/example-new/endpoint1, don't create an endpoint.

Here is the way I add endpoints.

add_action( 'init', 'add_new_e' );
add_filter( 'query_vars', 'filter_vars_e');
function add_new_e() {
    add_rewrite_endpoint( 'mash', EP_PAGES );
}

function filter_vars_e($vars) {
    $vars[] = 'mash';
    return $vars;
}

I am flushing rewrite rules when the plugin activates/deactivates.

Now the problem is when I open another page with an endpoint, it doesn't throw a 404 error, and I know that I am using the EP_PAGES mask.

Will someone help me with how I can achieve my goal.

Goal: add an endpoint to a specific page only having a specific template

Furthermore, I want to endpoints work in the same way as in woocommerce like my account page. Thanks in advance. If anybody needs other information please let me know.

Answer 1

No, add_rewrite_endpoint() doesn't limit to any specific page, only add_rewrite_rule() can do that.

However, if I understand it correctly, you can use the pre_handle_404 hook to check if the endpoint query is set and that the page uses a specific template, then throw a 404 error if those conditions are not met.

Working example based on your code:

add_filter( 'pre_handle_404', 'wpse_376370', 10, 2 );
function wpse_376370( $value, $wp_query ) {
    if (
        // It's a valid "mash" endpoint request,
        $wp_query->get( 'mash' )          &&
        // but the request is not a Page or its slug is not 'example',
        ! $wp_query->is_page( 'example' ) &&
        // and the Page is not using the template some-template.php.
        ! is_page_template( 'some-template.php' )
    ) {
        // Therefore, we throw a 404 error
        $wp_query->set_404();

        // and avoid redirect to the page. (at example.com/example)
        remove_action( 'template_redirect', 'redirect_canonical' );
    }

    return $value;
}