问WordPress动态菜单中的HTML/CSS下拉菜单

EN

class Custom_Nav_Walker extends Walker_Nav_Menu 
{
    /**
     * @var array $menu_items
     */
    private $menu_items;

    /**
     * @var int $last_menu_id
     */
    private $last_menu_id;

    /**
     * @var int $first_menu_id
     */
    private $first_menu_id;
    
    /**
     * @inheritdoc
     */
    public function start_el( &$output, $item, $depth = 0, $args = null, $id = 0 ) {

        if( is_null( $this->menu_items ) ) {

            $this->menu_items = wp_get_nav_menu_items( $args->theme_location );

            if( $this->menu_items != false ) {
                $first_menu_index = array_key_first( $this->menu_items );
                $last_menu_index = array_key_last( $this->menu_items );
                $this->first_menu_id = $this->menu_items[ $first_menu_index ]->ID;
                $this->last_menu_id = $this->menu_items[ $last_menu_index ]->ID;
            }
        }

        if ( isset( $args->item_spacing ) && 'discard' === $args->item_spacing ) {
            $t = '';
            $n = '';
        } else {
            $t = "\t";
            $n = "\n";
        }
        $indent = ( $depth ) ? str_repeat( $t, $depth ) : '';

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

        /**
         * Filters the arguments for a single nav menu item.
         *
         * @since 4.4.0
         *
         * @param stdClass $args  An object of wp_nav_menu() arguments.
         * @param WP_Post  $item  Menu item data object.
         * @param int      $depth Depth of menu item. Used for padding.
         */
        $args = apply_filters( 'nav_menu_item_args', $args, $item, $depth );

        /**
         * Filters the CSS classes applied to a menu item's list item element.
         *
         * @since 3.0.0
         * @since 4.1.0 The `$depth` parameter was added.
         *
         * @param string[] $classes Array of the CSS classes that are applied to the menu item's `<li>` element.
         * @param WP_Post  $item    The current menu item.
         * @param stdClass $args    An object of wp_nav_menu() arguments.
         * @param int      $depth   Depth of menu item. Used for padding.
         */

        $class_names = apply_filters( 'nav_menu_css_class', array_filter( $classes ), $item, $args, $depth );
        
        $custom_menu_class = [ 'nav-item' ];
        if( in_array( 'current-menu-item', $class_names ) ) {
            $custom_menu_class[] = 'active';
        }

        $class_names = implode( ' ',  $custom_menu_class);

        if( $item->ID == $this->last_menu_id ) {
            $class_names = ' class="last"';
        } else {
            $class_names = $class_names ? ' class="' . esc_attr( $class_names ) . '"' : '';
        }

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

        $atts           = array();
        $atts['title']  = ! empty( $item->attr_title ) ? $item->attr_title : '';
        $atts['target'] = ! empty( $item->target ) ? $item->target : '';
        if ( '_blank' === $item->target && empty( $item->xfn ) ) {
            $atts['rel'] = 'noopener';
        } else {
            $atts['rel'] = $item->xfn;
        }
        $atts['href']         = ! empty( $item->url ) ? $item->url : '';
        $atts['aria-current'] = $item->current ? 'page' : '';
        
        

        /**
         * Filters the HTML attributes applied to a menu item's anchor element.
         *
         * @since 3.6.0
         * @since 4.1.0 The `$depth` parameter was added.
         *
         * @param array $atts {
         *     The HTML attributes applied to the menu item's `<a>` element, empty strings are ignored.
         *
         *     @type string $title        Title attribute.
         *     @type string $target       Target attribute.
         *     @type string $rel          The rel attribute.
         *     @type string $href         The href attribute.
         *     @type string $aria_current The aria-current attribute.
         * }
         * @param WP_Post  $item  The current menu item.
         * @param stdClass $args  An object of wp_nav_menu() arguments.
         * @param int      $depth Depth of menu item. Used for padding.
         */
        $atts = apply_filters( 'nav_menu_link_attributes', $atts, $item, $args, $depth );

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

        /** This filter is documented in wp-includes/post-template.php */
        $title = apply_filters( 'the_title', $item->title, $item->ID );

        /**
         * Filters a menu item's title.
         *
         * @since 4.4.0
         *
         * @param string   $title The menu item's title.
         * @param WP_Post  $item  The current menu item.
         * @param stdClass $args  An object of wp_nav_menu() arguments.
         * @param int      $depth Depth of menu item. Used for padding.
         */
        $title = apply_filters( 'nav_menu_item_title', $title, $item, $args, $depth );

        if(  $item->ID == $this->last_menu_id ) {
            $item_output  = '<a href="#"><img src="images/search-icon.png" alt="icon"></a>';
        } else if ( $item->ID == $this->first_menu_id ) {
            $item_output  = $args->before;
            $item_output .= '<a' . $attributes . '>';
            $item_output .= $args->link_before . $title . '<span class="sr-only">(current)</span>';
            $item_output .= '</a>';
            $item_output .= $args->after;
        } else {
            $item_output  = $args->before;
            $item_output .= '<a' . $attributes . '>';
            $item_output .= $args->link_before . $title . $args->link_after;
            $item_output .= '</a>';
            $item_output .= $args->after;
        }

        /**
         * Filters a menu item's starting output.
         *
         * The menu item's starting output only includes `$args->before`, the opening `<a>`,
         * the menu item's title, the closing `</a>`, and `$args->after`. Currently, there is
         * no filter for modifying the opening and closing `<li>` for a menu item.
         *
         * @since 3.0.0
         *
         * @param string   $item_output The menu item's starting HTML output.
         * @param WP_Post  $item        Menu item data object.
         * @param int      $depth       Depth of menu item. Used for padding.
         * @param stdClass $args        An object of wp_nav_menu() arguments.
         */
        $output .= apply_filters( 'walker_nav_menu_start_el', $item_output, $item, $depth, $args );
    }
}

wp_nav_menu(
    array(
        'theme_location'    => 'your theme location',
        'echo'              => true,
        'walker' => new Custom_Nav_Walker(),
        'menu_class' => 'navbar-nav mr-auto'
    )
);