nickbowman

I don’t know if this is the correct solution, but in case anyone stumbles across this and has the same problem, this is what I did to fix it.

add_filter( 'page_link', 'modify_item_page_permalink', 10, 3 );

function modify_item_page_permalink( $url, $pageid, $sample ) {
	global $wp_query;
	if ( get_the_ID() == $pageid ) {
		if ( ! empty( $wp_query->query_vars['item_id'] ) ) {
			$url .= $wp_query->query_vars['item_id'] . '/';
		}
	}
	return $url;
}

The page_link action isn’t documented. Use post_link if you’re not using a page.

Checking to see if the $pageid == get_the_ID() is to prevent it from adding these querystrings onto navigation links.