Handler for updating the current site’s posts count when a post status changes.

function _update_posts_count_on_transition_post_status( $new_status, $old_status, $post = null ) {
	if ( $new_status === $old_status ) {
		return;
	}

	if ( 'post' !== get_post_type( $post ) ) {
		return;
	}

	if ( 'publish' !== $new_status && 'publish' !== $old_status ) {
		return;
	}

	update_posts_count();
}