@drew321 Probably, you want use “option” for the $post_id but I can’t be specific without more details. Maybe I’m wrong.
For your question about fetch: fetch is like Ajax and it’s appear with modern browsers. Its JavaScript, not WordPress or PHP. You can put a look on this page for quick details: https://www.w3schools.com/js/js_ajax_intro.asp (scroll to bottom of the page for fetch info instead of Ajax)
But with WordPress, you can manage Ajax/Fetch with security. With the wp_ajax_{action} hook. Put a look here: https://developer.wordpress.org/reference/hooks/wp_ajax_action/
