WordPress Menu Walker to generate Uikit Navbar and Nav components from simple menu

LhL_uikit_walker.php

<?php

class LhL_uikit_walker extends Walker_Nav_Menu {

    private $menu_type;

    function __construct($type) {
        $this->menu_type = $type;
    }

    /**
     * Starts the list before the elements are added. 
     *
     * Adds classes to the unordered list sub-menus.
     *
     * @param string $output Passed by reference. Used to append additional content.
     * @param int    $depth  Depth of menu item. Used for padding.
     * @param array  $args   An array of arguments. @see wp_nav_menu()
     */
    function start_lvl( &$output, $depth = 0, $args = array() ) {

        // Depth-dependent classes.
        $indent = ( $depth > 0  ? str_repeat( "\t", $depth ) : '' ); // code indent

        $display_depth = ( $depth + 1); // because it counts the first submenu as 0

        $classes = array(
            'sub-menu',
            ($this->menu_type == 'navbar' ? 'uk-nav uk-navbar-dropdown-nav' : 'uk-nav-sub'),
            ( $display_depth % 2  ? 'menu-odd' : 'menu-even' ),
            ( $display_depth >=2 ? 'sub-sub-menu' : '' ),
            'menu-depth-' . $display_depth
        );

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

        $ul_wrapper_div = "";
        if($this->menu_type == 'navbar'){
            $ul_wrapper_div = $display_depth >=1 ? '<div class="uk-navbar-dropdown">' : '';
        }                    

        // Build HTML for output.
        $output .= "\n" . $indent . $ul_wrapper_div . '<ul class="' . $class_names . '">' . "\n";
    }


    /**
     * Ends the list of after 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 stdClass $args   An object of wp_nav_menu() arguments.
     */

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

        if ( isset( $args->item_spacing ) && 'discard' === $args->item_spacing ) {
            $t = '';
            $n = '';
        } else {
            $t = "\t";
            $n = "\n";
        }
        $display_depth = ( $depth + 1);

        $ul_wrapper_div_end = '';
        if($this->menu_type == 'navbar'){
            $ul_wrapper_div_end = $display_depth >=1 ? '</div>' : '';
        }

        $indent  = str_repeat( $t, $depth );
        $output .= "$indent" . "</ul>" . "$ul_wrapper_div_end" . "{$n}";
        
    }

    /**
     * Start the element output.
     *
     * Adds main/sub-classes to the list items and links.
     *
     * @param string $output Passed by reference. Used to append additional content.
     * @param object $item   Menu item data object.
     * @param int    $depth  Depth of menu item. Used for padding.
     * @param array  $args   An array of arguments. @see wp_nav_menu()
     * @param int    $id     Current item ID.
     */
    function start_el( &$output, $item, $depth = 0, $args = array(), $id = 0 ) {
        // 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 ) );

        // var_dump($item);

        // 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 ) ) );

        // for NAV type parent Li-s need uk-parent class
        if($this->menu_type == 'nav'){
            if($args->walker->has_children){
                $class_names .= ' uk-parent';
            }
        }

        // Build HTML.
        $output .= $indent . '<li id="nav-menu-item-'. $item->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' ) . '"';

        switch ($item->title) {
            case 'Search':
                $link_title = "<img type='image' alt='Search' src='" . get_template_directory_uri() . "/images/search.png' />";
                $attributes .= 'uk-toggle="target: #searchform; animation: uk-animation-fade"';
                break;
            
            default:
                $link_title = apply_filters( 'the_title', $item->title, $item->ID );
                break;
        }

        // Build HTML output and pass through the proper filter.
        $item_output = sprintf( '%1$s<a%2$s>%3$s%4$s%5$s</a>%6$s',
            $args->before,
            $attributes,
            $args->link_before,
            $link_title,
            $args->link_after,
            $args->after
        );
        $output .= apply_filters( 'walker_nav_menu_start_el', $item_output, $item, $depth, $args );
    }

}


/**
 * For regular Navigation use the following
 * https://getuikit.com/docs/navbar
 */

/*
    wp_nav_menu( array( 
        'container' => 'ul',
        'menu_class' => 'uk-navbar-nav',
        'theme_location' => 'YOUR_MENU_LOCATION',
        'depth' => 2,
        'walker' => new Lhl_uikit_walker("navbar"),
    ) );
*/


/**
 * For regular Navigation use the following
 * https://getuikit.com/docs/nav
 */

/*
    wp_nav_menu( array( 
        'container'       => '<div>',
        'menu_class' => 'uk-nav-primary uk-nav-parent-icon ',
        'items_wrap'      => '<ul id="%1$s" class="%2$s" uk-nav>%3$s</ul>',
        'theme_location' => 'YOUR_MENU_LOCATION',
        'depth' => 2,
        'walker' => new Lhl_uikit_walker("nav"),
    ) );
*/

?>