public function ajax_load_available_items() {
		check_ajax_referer( 'customize-menus', 'customize-menus-nonce' );

		if ( ! current_user_can( 'edit_theme_options' ) ) {
			wp_die( -1 );
		}

		$all_items  = array();
		$item_types = array();
		if ( isset( $_POST['item_types'] ) && is_array( $_POST['item_types'] ) ) {
			$item_types = wp_unslash( $_POST['item_types'] );
		} elseif ( isset( $_POST['type'] ) && isset( $_POST['object'] ) ) { // Back compat.
			$item_types[] = array(
				'type'   => wp_unslash( $_POST['type'] ),
				'object' => wp_unslash( $_POST['object'] ),
				'page'   => empty( $_POST['page'] ) ? 0 : absint( $_POST['page'] ),
			);
		} else {
			wp_send_json_error( 'nav_menus_missing_type_or_object_parameter' );
		}

		foreach ( $item_types as $item_type ) {
			if ( empty( $item_type['type'] ) || empty( $item_type['object'] ) ) {
				wp_send_json_error( 'nav_menus_missing_type_or_object_parameter' );
			}
			$type   = sanitize_key( $item_type['type'] );
			$object = sanitize_key( $item_type['object'] );
			$page   = empty( $item_type['page'] ) ? 0 : absint( $item_type['page'] );
			$items  = $this->load_available_items_query( $type, $object, $page );
			if ( is_wp_error( $items ) ) {
				wp_send_json_error( $items->get_error_code() );
			}
			$all_items[ $item_type['type'] . ':' . $item_type['object'] ] = $items;
		}

		wp_send_json_success( array( 'items' => $all_items ) );
	}