wp nav walker class

<?php
/**
 * Custom Navigation Walker
 *
 * This class extends WordPress's Walker_Nav_Menu to customize the HTML output
 * of navigation menus. It adds Bootstrap classes and custom attributes.
 */
class Custom_Nav_Walker extends Walker_Nav_Menu {
    /**
     * Starts the list before the elements are added.
     *
     * @param string $output Used to append additional content (passed by reference).
     * @param int    $depth  Depth of menu item. Used for padding.
     * @param array  $args   An array of arguments.
     */
    public function start_lvl(&$output, $depth = 0, $args = null) {
        $indent = str_repeat("\t", $depth);
        $submenu = ($depth > 0) ? ' sub-menu' : '';
        $output .= "\n$indent<ul class=\"dropdown-menu$submenu\">\n";
    }

    /**
     * Starts the element output.
     *
     * @param string $output Used to append additional content (passed by reference).
     * @param object $item   Menu item data object.
     * @param int    $depth  Depth of menu item.
     * @param array  $args   An array of arguments.
     * @param int    $id     Current item ID.
     */
    public function start_el(&$output, $item, $depth = 0, $args = null, $id = 0) {
        $indent = ($depth) ? str_repeat("\t", $depth) : '';

        $classes = empty($item->classes) ? array() : (array) $item->classes;
        $classes[] = 'menu-item-' . $item->ID;

        // Add Bootstrap dropdown class if item has children
        if ($args->walker->has_children) {
            $classes[] = 'dropdown';
        }

        $class_names = join(' ', apply_filters('nav_menu_css_class', array_filter($classes), $item, $args));
        $class_names = $class_names ? ' class="' . esc_attr($class_names) . '"' : '';

        $id = apply_filters('nav_menu_item_id', 'menu-item-' . $item->ID, $item, $args);
        $id = $id ? ' id="' . esc_attr($id) . '"' : '';

        $output .= $indent . '<li' . $id . $class_names . '>';

        $atts = array();
        $atts['title']  = !empty($item->attr_title) ? $item->attr_title : '';
        $atts['target'] = !empty($item->target) ? $item->target : '';
        $atts['rel']    = !empty($item->xfn) ? $item->xfn : '';
        $atts['href']   = !empty($item->url) ? $item->url : '';

        // Add Bootstrap dropdown attributes if item has children
        if ($args->walker->has_children) {
            $atts['class']         = 'dropdown-toggle';
            $atts['data-toggle']   = 'dropdown';
            $atts['aria-haspopup'] = 'true';
            $atts['aria-expanded'] = 'false';
        }

        $atts = apply_filters('nav_menu_link_attributes', $atts, $item, $args);

        $attributes = '';
        foreach ($atts as $attr => $value) {
            if (!empty($value)) {
                $value = ('href' === $attr) ? esc_url($value) : esc_attr($value);
                $attributes .= ' ' . $attr . '="' . $value . '"';
            }
        }

        $title = apply_filters('the_title', $item->title, $item->ID);
        $title = apply_filters('nav_menu_item_title', $title, $item, $args, $depth);

        $item_output = $args->before;
        $item_output .= '<a' . $attributes . '>';
        $item_output .= $args->link_before . $title . $args->link_after;
        
        // Add dropdown arrow for items with children
        if ($args->walker->has_children) {
            $item_output .= ' <span class="dropdown-arrow"></span>';
        }
        
        $item_output .= '</a>';
        $item_output .= $args->after;

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

    /**
     * Ends the element output.
     *
     * @param string $output Used to append additional content (passed by reference).
     * @param object $item   Menu item data object.
     * @param int    $depth  Depth of menu item.
     * @param array  $args   An array of arguments.
     */
    public function end_el(&$output, $item, $depth = 0, $args = null) {
        $output .= "</li>\n";
    }
}

// Example usage in functions.php:
function register_custom_nav_walker() {
    require_once get_template_directory() . '/class-custom-nav-walker.php';
}
add_action('after_setup_theme', 'register_custom_nav_walker');

// Example usage in template file:
wp_nav_menu(array(
    'theme_location' => 'primary',
    'depth'          => 2,
    'container'      => 'nav',
    'container_class'=> 'navbar-collapse',
    'menu_class'     => 'nav navbar-nav',
    'walker'         => new Custom_Nav_Walker()
));

案例

<?php 
// Custom Walker Class
class Bootstrap_Nav_Walker extends Walker_Nav_Menu {

    public function start_lvl(&$output, $depth = 0, $args = null) {

        $indent = str_repeat("\t", $depth);
        $output .= "\n$indent<ul class=\"dropdown-menu\">\n";

    }

    public function start_el(&$output, $item, $depth = 0, $args = null, $id = 0) {

        $indent = ($depth) ? str_repeat("\t", $depth) : '';
        
        $classes = empty($item->classes) ? array() : (array) $item->classes;
        $classes[] = 'nav-item';

        
        // Add dropdown class if li item has children
        if ($args->walker->has_children) {
            $classes[] = 'dropdown';
            $classes[] = 'pc';
        }
        
        $class_names = join(' ', apply_filters('nav_menu_css_class', array_filter($classes), $item, $args));

        $class_names = $class_names ? ' class="' . esc_attr($class_names) . '"' : '';
        
        $output .= $indent . '<li' . $class_names . '>';
        
        $atts = array();
        $atts['href'] = !empty($item->url) ? $item->url : '';
        $atts['class'] = 'nav-link';

         if ($depth === 0) {
            $atts['class'] = 'nav-link';
            if ($args->walker->has_children) {
                $atts['class'] .= ' dropdown-toggle';
            }
        } else {
            $atts['class'] = 'dropdown-item';
        }

        $attributes = '';
        foreach ($atts as $attr => $value) {
            if (!empty($value)) {
                $value = ('href' === $attr) ? esc_url($value) : esc_attr($value);
                $attributes .= ' ' . $attr . '="' . $value . '"';
            }
        }
        
        $title = apply_filters('the_title', $item->title, $item->ID);
        
        $item_output = $args->before;
        $item_output .= '<a' . $attributes . '>';
        $item_output .= $args->link_before . $title . $args->link_after;
        $item_output .= '</a>';
        $item_output .= $args->after;
        
        $output .= apply_filters('walker_nav_menu_start_el', $item_output, $item, $depth, $args);


    }
}