[WordPress Plugin] Nav Menu Exporter and Importer / Export and Import nav menus. Requires WordPress Importer plugin.

nav-menu-exporter-importer.php

<?php
/*
Plugin Name: Nav Menu Exporter and Importer
Description: Export and Import nav menus. Requires WordPress Importer plugin
Author: hissy, megumi themes
Version: 0.1
Text Domain: nav-menu-exporter-importer
License: GPL version 2 or later - http://www.gnu.org/licenses/old-licenses/gpl-2.0.html
*/


/**
 * Exporter
 */
function add_mav_menu_to_export() {
	$post_type = get_post_type_object('nav_menu_item');
	?>
	<p><label><input type="radio" name="content" value="<?php echo esc_attr( $post_type->name ); ?>" /> <?php echo esc_html( $post_type->label ); ?></label></p>
	<?php
}
add_action('export_filters','add_mav_menu_to_export');


/**
 * Importer
 */
if ( ! defined( 'WP_LOAD_IMPORTERS' ) )
	return;

// Load Importer API
require_once ABSPATH . 'wp-admin/includes/import.php';

if ( ! class_exists( 'WP_Importer' ) ) {
	$class_wp_importer = ABSPATH . 'wp-admin/includes/class-wp-importer.php';
	if ( file_exists( $class_wp_importer ) )
		require $class_wp_importer;
}

// include WXR file parsers
$wordpress_importer = ABSPATH . 'wp-content/plugins/wordpress-importer/wordpress-importer.php';
if ( file_exists( $wordpress_importer ) )
	require_once $wordpress_importer;

/**
 * Nav Menu Importer class
 */
if ( class_exists( 'WP_Import' ) ) {
class Nav_Menu_Importer extends WP_Import {

	function dispatch() {
		$this->header();

		$step = empty( $_GET['step'] ) ? 0 : (int) $_GET['step'];
		switch ( $step ) {
			case 0:
				$this->greet();
				break;
			case 1:
				check_admin_referer( 'import-upload' );
				if ( $this->handle_upload() ) {
					$file = get_attached_file( $this->id );
					set_time_limit(0);
					$this->import( $file );
				}
				break;
		}

		$this->footer();
	}
	
	function greet() {
		wp_import_upload_form( add_query_arg('step', 1) );
	}
	
	function import_end() {
		wp_import_cleanup( $this->id );

		wp_cache_flush();

		echo '<p>' . __( 'All done.', 'wordpress-importer' ) . ' <a href="' . admin_url() . '">' . __( 'Have fun!', 'wordpress-importer' ) . '</a>' . '</p>';
	}
	
	function import( $file ) {
		$this->import_start( $file );

		wp_suspend_cache_invalidation( true );
		// only processing nav menus
		$this->process_menus();
		wp_suspend_cache_invalidation( false );

		$this->import_end();
	}
	
	function process_menus() {
		$count = 0;
		
		foreach ( $this->posts as $item ) {
			$count++;

			// check the item is public nav item
			if ( 'nav_menu_item' == $item['post_type'] && 'draft' != $item['status'] ) {
				
				$menu_slug = false;
				if ( isset($item['terms']) ) {
					// loop through terms, assume first nav_menu term is correct menu
					foreach ( $item['terms'] as $term ) {
						if ( 'nav_menu' == $term['domain'] ) {
							$menu_slug = $term['slug'];
							break;
						}
					}
				}

				// no nav_menu term associated with this menu item
				if ( ! $menu_slug ) {
					_e( 'Menu item skipped due to missing menu slug', 'wordpress-importer' );
					echo '<br>';
					continue;
				}
		
				$menu_id = term_exists( $menu_slug, 'nav_menu' );
				if ( ! $menu_id ) {
					printf( __( 'Menu item skipped due to invalid menu slug: %s', 'wordpress-importer' ), esc_html( $menu_slug ) );
					echo '<br>';
					continue;
				} else {
					$menu_id = is_array( $menu_id ) ? $menu_id['term_id'] : $menu_id;
				}
				
				// set postmeta
				foreach ( $item['postmeta'] as $meta )
					$$meta['key'] = $meta['value'];
				
				// skip nav item when menu item object is not exists
				switch ($_menu_item_type) {
					case 'taxonomy':
						$_menu_item_object_id = get_term($_menu_item_object_id,$_menu_item_object);
						if ($_menu_item_object_id == null || is_wp_error($_menu_item_object_id)) {
							printf( __( 'Menu item skipped due to %s is not exists', 'nav-menu-exporter-importer' ), esc_html( $_menu_item_object ) );
							echo '<br>';
						}
						break;
					case 'post_type':
						$_menu_item_object_id = get_post($_menu_item_object_id);
						if ($_menu_item_object_id instanceof WP_Post) {
							$_menu_item_object_id = $_menu_item_object_id->ID;
							unset($_post);
						} else {
							printf( __( 'Menu item skipped due to %s is not exists', 'nav-menu-exporter-importer' ), esc_html( $_menu_item_object ) );
							echo '<br>';
						}
						break;
				}
				
				if ($_menu_item_object_id == null || is_wp_error($_menu_item_object_id))
					continue;
				
				// wp_update_nav_menu_item expects CSS classes as a space separated string
				$_menu_item_classes = maybe_unserialize( $_menu_item_classes );
				if ( is_array( $_menu_item_classes ) )
					$_menu_item_classes = implode( ' ', $_menu_item_classes );

				$args = array(
					'menu-item-object-id' => $_menu_item_object_id,
					'menu-item-object' => $_menu_item_object,
					'menu-item-parent-id' => $_menu_item_menu_item_parent,
					'menu-item-position' => intval( $item['menu_order'] ),
					'menu-item-type' => $_menu_item_type,
					'menu-item-title' => $item['post_title'],
					'menu-item-url' => $_menu_item_url,
					'menu-item-description' => $item['post_content'],
					'menu-item-attr-title' => $item['post_excerpt'],
					'menu-item-target' => $_menu_item_target,
					'menu-item-classes' => $_menu_item_classes,
					'menu-item-xfn' => $_menu_item_xfn,
					'menu-item-status' => $item['status']
				);
		
				$r = wp_update_nav_menu_item( $menu_id, 0, $args );
				
				if ( $r && is_wp_error( $r ) ) {
					echo $r->get_error_message();
					echo '<br>';
				} else {
					echo '.';
				}
				
			}
			
		}
		
		echo '<br>';
		printf( __( '%s items processed.', 'nav-menu-exporter-importer' ), esc_html( $count ) );
	}

}

// setup importer
$nav_menu_importer = new Nav_Menu_Importer();

register_importer('nav_menu', __('Nav Menu', 'nav-menu-exporter-importer'), __('Export and Import nav menus. Requires WordPress Importer plugin', 'nav-menu-exporter-importer'), array ($nav_menu_importer, 'dispatch'));

} // class_exists( 'WP_Import' )

I made some fix and modification, with WordPress 4.7 in my dev enviroments it works fine with tax, post_type and custom nav menu items and now if the menu doesn't exist it will be created during the import.
Here the link https://gist.github.com/overclokk/bad83a7cb3db4263192aa52db0a60fc0

Hello,

can I use this Tool to migrate from one Domain www.123.com to another Domain www.abc.de
How can I do this?

The pages are the same on both Domains.

I´ve renamed in domains inside the export file to the new domain, but I got this error:

Menu item skipped due to invalid menu slug: primary

Best regards,

Rene

It is unfortunate but this tool does not work in multisite.

how to use this 'plugin'?

there is no guide or instructions about how to 'install' this

save the file as nav-menu-exporter-importer.php and put into wp-content/plugins/wordpress-importer directory. then go into Plugins in Admin Dashboard to activate

Hi,
Almost working.
Export is OK (do not update Nav Menu Exporter and Importer).
Import run well (create a menu with same name before) : 87 items processed. But menu is empty.
Anyway thank you,