CMB2 show_on helper functions ( show_on_front_page, show_on_subpage)

cmb2-show-on-helpers

/**
 * Helper function to check if we edit front page
 * @param type $cmb
 * @param type $cmb
 * @return type
 */
function cmb2_show_if_front_page( $cmb ) {
	// Don't show this metabox if it's not the front page template
	if ( $cmb->object_id !== get_option( 'page_on_front' ) ) {
		return false;
	}
	return true;
}

/**
 * Helper function to check if we edit subpage (child page)
 * @param type $cmb
 * @param type $cmb
 * @return type
 */
function cmb2_show_on_subpage( $cmb ) {
	$post_id = 0;

	// If we're showing it based on ID, get the current ID
    if ( isset( $_GET['post'] ) ) {
        $post_id = $_GET['post'];
    } elseif ( isset( $_POST['post_ID'] ) ) {
        $post_id = $_POST['post_ID'];
    }

    // If the post does have ancestors, show the box
    if ( get_post_ancestors( $post_id ) ) {
        return true;
    }

	return false;
}