Any walker causes blank menu? in WordPress

Using the following, or any other custom Walker_Nav_Menu seems to cause a blank navigation menu, I tried specifying the default to make sure I wasn’t going crazy yet it still blanks the output… Any ideas on what is going wrong?

<?php wp_nav_menu( array( 'theme_location' => 'primary', 'depth' => 3, 'walker' => new Walker_Nav_Menu() ) ); ?>

In Context

<?php
/**
 * The Header for our theme.
 *
 * Displays all of the <head> section and everything up till <div id="main">
 *
 * @package Expound
 */
?><!DOCTYPE html>
<html <?php language_attributes(); ?>>
<head>
<meta charset="<?php bloginfo( 'charset' ); ?>" />
<meta name="viewport" content="width=device-width, initial-scale=1" />
<title><?php wp_title( '|', true, 'right' ); ?></title>
<link rel="profile" href="http://gmpg.org/xfn/11" />
<link rel="pingback" href="<?php bloginfo( 'pingback_url' ); ?>" />
<!--[if lt IE 9]>
<script src="<?php echo get_template_directory_uri(); ?>/js/html5.js" type="text/javascript"></script>
<![endif]-->

<?php wp_head(); ?>
</head>

<body <?php body_class(); ?>>
<div id="page" class="hfeed site">
    <?php do_action( 'expound_header_before' ); ?>
    <header id="masthead" class="site-header" role="banner">
        <div class="site-branding">
            <div class="site-title-group">
                <a href="<?php echo esc_url( home_url( '/' ) ); ?>" title="<?php echo esc_attr( get_bloginfo( 'name', 'display' ) ); ?>" rel="home">
                    <!--div class="site-title"><!--?php bloginfo( 'name' ); ?></div-->
                    <img height="240" width="722" alt="The All Australian Minecraft Community" class="wp-post-image" src="http://taamc.com/wordpress/wp-content/themes/expound-child/images/logo.png">
                    <!--h2 class="site-description"--><!--?php bloginfo( 'description' ); ?--><!--/h2-->
                    <!--div id="sub-title">
                        <div id="sub-title-image"></div>
                    </div-->
                </a>
            </div>
        </div>
        <div class = "site-title-group">
                <?php if ( dynamic_sidebar('header_widget_area') ) : else : endif; ?>
        </div>
        <nav id="site-navigation" class="navigation-main" role="navigation">
            <h1 class="menu-toggle"><?php _e( 'Menu', 'expound' ); ?></h1>
            <div class="screen-reader-text skip-link"><a href="#content" title="<?php esc_attr_e( 'Skip to content', 'expound' ); ?>"><?php _e( 'Skip to content', 'expound' ); ?></a></div>
####################################################################################    
<?php wp_nav_menu( array( 'theme_location' => 'primary', 'depth' => 3, 'walker' => new Walker_Nav_Menu()) ); ?>
####################################################################################
            <div class="site-nav-search"><?php if ( dynamic_sidebar('navigation_widget_area') ) : else : endif; ?></div>
            <?php do_action( 'expound_navigation_after' ); ?>
        </nav><!-- #site-navigation -->
    </header><!-- #masthead -->
    <?php do_action( 'expound_header_after' ); ?>

    <div id="main" class="site-main">

The above is currently in my header.php of a child theme if that makes any difference, and the original theme also used the default walker, however it wasn’t explicitly stated.

with php as above

        <div class="menu">
            <ul class=" nav-menu">
            <li class="current_page_item">
                <a href="http://taamc.com/">Home</a>
            </li>
            <li id="menu-item-21" class="menu-item-21">
                <a></a>
            </li>
            <li id="menu-item-87" class="menu-item-87">
                <a></a>
            </li>
            <li id="menu-item-122" class="menu-item-122">
                <a></a>
            </li>
            <li id="menu-item-28" class="menu-item-28">
                <a></a>
            </li>
            <li id="menu-item-127" class="menu-item-127">
                <a></a>
            </li>
            <li id="menu-item-22" class="menu-item-22">
                <a></a>
            </li>
        </ul>
    </div>

Gives errors:

Notice: Trying to get property of non-object in /home/taamc/public_html/wordpress/wp-includes/nav-menu-template.php on line 148

Notice: Trying to get property of non-object in /home/taamc/public_html/wordpress/wp-includes/nav-menu-template.php on line 151

Notice: Trying to get property of non-object in /home/taamc/public_html/wordpress/wp-includes/nav-menu-template.php on line 151

Notice: Trying to get property of non-object in /home/taamc/public_html/wordpress/wp-includes/nav-menu-template.php on line 153

Notice: Trying to get property of non-object in /home/taamc/public_html/wordpress/wp-includes/nav-menu-template.php on line 148

Notice: Trying to get property of non-object in /home/taamc/public_html/wordpress/wp-includes/nav-menu-template.php on line 151

Notice: Trying to get property of non-object in /home/taamc/public_html/wordpress/wp-includes/nav-menu-template.php on line 151

Notice: Trying to get property of non-object in /home/taamc/public_html/wordpress/wp-includes/nav-menu-template.php on line 153

Notice: Trying to get property of non-object in /home/taamc/public_html/wordpress/wp-includes/nav-menu-template.php on line 148

Notice: Trying to get property of non-object in /home/taamc/public_html/wordpress/wp-includes/nav-menu-template.php on line 151

Notice: Trying to get property of non-object in /home/taamc/public_html/wordpress/wp-includes/nav-menu-template.php on line 151

Notice: Trying to get property of non-object in /home/taamc/public_html/wordpress/wp-includes/nav-menu-template.php on line 153

Notice: Trying to get property of non-object in /home/taamc/public_html/wordpress/wp-includes/nav-menu-template.php on line 148

Notice: Trying to get property of non-object in /home/taamc/public_html/wordpress/wp-includes/nav-menu-template.php on line 151

Notice: Trying to get property of non-object in /home/taamc/public_html/wordpress/wp-includes/nav-menu-template.php on line 151

Notice: Trying to get property of non-object in /home/taamc/public_html/wordpress/wp-includes/nav-menu-template.php on line 153

Notice: Trying to get property of non-object in /home/taamc/public_html/wordpress/wp-includes/nav-menu-template.php on line 148

Notice: Trying to get property of non-object in /home/taamc/public_html/wordpress/wp-includes/nav-menu-template.php on line 151

Notice: Trying to get property of non-object in /home/taamc/public_html/wordpress/wp-includes/nav-menu-template.php on line 151

Notice: Trying to get property of non-object in /home/taamc/public_html/wordpress/wp-includes/nav-menu-template.php on line 153

Notice: Trying to get property of non-object in /home/taamc/public_html/wordpress/wp-includes/nav-menu-template.php on line 148

Notice: Trying to get property of non-object in /home/taamc/public_html/wordpress/wp-includes/nav-menu-template.php on line 151

Notice: Trying to get property of non-object in /home/taamc/public_html/wordpress/wp-includes/nav-menu-template.php on line 151

Notice: Trying to get property of non-object in /home/taamc/public_html/wordpress/wp-includes/nav-menu-template.php on line 153

with php as found by default in the theme

<?php wp_nav_menu( array( 'theme_location' => 'primary', 'depth' => 3) ); ?>

<div class="menu">
    <ul class=" nav-menu">
    <li class="current_page_item">
        <a href="http://taamc.com/">Home</a>
    </li>
    <li class="page_item page-item-21">
        <a href="http://taamc.com/activity/">Activity</a>
    </li>
    <li class="page_item page-item-87">
        <a href="http://taamc.com/gallery/">Gallery</a>
    </li>
    <li class="page_item page-item-122">
        <a href="http://taamc.com/getting-started/">Getting Started</a>
    </li>
    <li class="page_item page-item-28">
        <a href="http://taamc.com/groups/">Groups</a>
    </li>
    <li class="page_item page-item-127">
        <a href="http://taamc.com/map/">Map</a>
    </li>
    <li class="page_item page-item-22">
        <a href="http://taamc.com/members/">Members</a>
    </li>
    </ul>
</div>

Post Views: 1

I think the wholee problem is your trying to use the default walker, but by declaring it in the walker field your telling wordpress your trying to load a custom walker, the wp walker is loaded by default if left empty.

two options:

1/ change 'walker' => new Walker_Nav_Menu() to 'walker' => '' as its called by default.

2/ edit declaration to a new name like: new themeslug_Walker_Nav_Menu() then add the following to your function.php:

class themeslug_walker_nav_menu extends Walker_Nav_Menu {

// add classes to ul sub-menus
    function start_lvl( &$output, $depth ) {
        // depth dependent classes
        $indent = ( $depth > 0  ? str_repeat( "t", $depth ) : '' ); // code indent
        $display_depth = ( $depth + 1); // because it counts the first submenu as 0
        $classes = array(
            'sub-menu',
            ( $display_depth % 2  ? 'menu-odd' : 'menu-even' ),
            ( $display_depth >=2 ? 'sub-sub-menu' : '' ),
            'menu-depth-' . $display_depth
            );
        $class_names = implode( ' ', $classes );

        // build html
        $output .= "n" . $indent . '' . "n";
    }

    // add main/sub classes to li's and links
     function start_el( &$output, $item, $depth, $args ) {
        global $wp_query;
        $indent = ( $depth > 0 ? str_repeat( "t", $depth ) : '' ); // code indent

        // depth dependent classes
        $depth_classes = array(
            ( $depth == 0 ? 'main-menu-item' : 'sub-menu-item' ),
            ( $depth >=2 ? 'sub-sub-menu-item' : '' ),
            ( $depth % 2 ? 'menu-item-odd' : 'menu-item-even' ),
            'menu-item-depth-' . $depth
        );
        $depth_class_names = esc_attr( implode( ' ', $depth_classes ) );

        // passed classes
        $classes = empty( $item->classes ) ? array() : (array) $item->classes;
        $class_names = esc_attr( implode( ' ', apply_filters( 'nav_menu_css_class', array_filter( $classes ), $item ) ) );

        // build html
        $output .= $indent . 'ID . '" class="' . $depth_class_names . ' ' . $class_names . '">';

        // link attributes
        $attributes  = ! empty( $item->attr_title ) ? ' title="'  . esc_attr( $item->attr_title ) .'"' : '';
        $attributes .= ! empty( $item->target )     ? ' target="' . esc_attr( $item->target     ) .'"' : '';
        $attributes .= ! empty( $item->xfn )        ? ' rel="'    . esc_attr( $item->xfn        ) .'"' : '';
        $attributes .= ! empty( $item->url )        ? ' href="'   . esc_attr( $item->url        ) .'"' : '';
        $attributes .= ' class="menu-link ' . ( $depth > 0 ? 'sub-menu-link' : 'main-menu-link' ) . '"';

        $item_output = sprintf( '%1$s%3$s%4$s%5$s%6$s',
            $args->before,
            $attributes,
            $args->link_before,
            apply_filters( 'the_title', $item->title, $item->ID ),
            $args->link_after,
            $args->after
        );

        // build html
        $output .= apply_filters( 'walker_nav_menu_start_el', $item_output, $item, $depth, $args );
    }
}

see the codex its explains quite well.

6 comments

Anonymous says:

June 18, 2023 at 2:49 pm
You need to make sure your menu is properly registered in your functions.php and then activated in the WP Dashboard.
```
add_action( 'init', register_nav_menu( 'navigation', __( 'Navigation' ) ) );
```
Otherwise I was just facing a long list of empty bullet points.

http://codex.wordpress.org/Navigation_Menus
Anonymous says:

June 18, 2023 at 2:49 pm
You should pass an actual object as ‘walker’ – not create one on the fly. The correct way to do it is:
```
$myWalker = new Walker_Nav_Menu();
wp_nav_menu( array( 'theme_location' => 'primary', 'depth' => 3, 'walker' => $myWalker ) ); ?>
```
Also make sure you extend Walker_Nav_Menu in your custom class.

do you use walker menu for mobile responsive purpose ? If yes then you can go for an another solution.(Only if you cant fix your errors with the walker menu)

you can hide main menu on mobile devices and can use another one. here is an example

<div class="m-sec-nav">
        <?php 
        $menu_name = 'careers-menu'; //your menu theme_location
        if ( ( $locations = get_nav_menu_locations() ) && isset( $locations[ $menu_name ] ) ) {
                $menu = wp_get_nav_menu_object( $locations[ $menu_name ] );
                $menu_items = wp_get_nav_menu_items($menu->term_id); ?>
                    <select onchange="location = this.options[this.selectedIndex].value;">
                    <?php foreach ( (array) $menu_items as $key => $menu_item ) { ?>
                        <option value="<?php echo $menu_item->url; ?>"><?php echo $menu_item->title; ?></option>
                    <?php } ?>
                    </select>
                <?php } ?>

    </div>

Anonymous says:

June 18, 2023 at 2:49 pm

Sometimes this happens when a menu hasn’t been created yet. The reason you can’t use or extend the Walker_Nav_Menu class is because the actual menu that you see when you call upon the primary nav menu without a walker is actually the fallback to wp_page_menu(). For this to work with a walker, a menu will need to be created and the Primary checkbox will need to be checked.

Custom_Nav_Walker put `function.php` file

add_theme_support( 'nav-menus' );

class Custom_Nav_Walker extends Walker_Nav_Menu {

    function start_lvl(&$output, $depth = 0, $args = array()) {
        $output .= "n<div class="submenu">n";
    }

    function end_lvl(&$output, $depth = 0, $args = array()) {
        $output .= "n</div>n";
    }

    function start_el(&$output, $item, $depth = 0, $args = array(), $id = 0) {
        parent::start_el( $item_html, $item, $depth, $args );
        if ( $item->is_dropdown && ( $depth === 0 ) ) {
            $output .= "<a href="".esc_url($item->url)."">".esc_attr($item->title)."</a>";
        } elseif ($depth === 0) {
            $output .= "<a href="".esc_url($item->url)."">".esc_attr($item->title)."</a>";
        } elseif ($depth > 0) {
            $output .= "<a href="".esc_url($item->url)."">".esc_attr($item->title)."</a>";
        }
    }

nav_menu put `header.php`

<?php
$defaults = array(
    'theme_location'  => '',
    'menu'            => 'Project Nav', //menu name
    'container'       => false,
    'container_class' => ' ',
    'container_id'    => '',
    'menu_class'      => 'nav',
    'menu_id'         => '',
    'echo'            => true,
    'before'          => '',
    'after'           => '',
    'link_before'     => '',
    'link_after'      => '',
    'items_wrap'      => '<div id="%1$s" class="%2$s">%3$s</div>',
    'depth'           => 0,
    'walker'          => new Custom_Nav_Walker() 
);

wp_nav_menu( $defaults );
?>

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