where does this $post_id come from?
It comes from wp_insert_post(), where do_action() is called with two additional parameters: do_action(‘save_post’, $post_ID, $post); So it is not you who adds the parameters, it is WordPress. If you register your callback with the fourth parameter set to 2 … add_action( ‘save_post’, ‘mytestfunc’, 10, 2 ); … you will even get the complete $post object: … Read more