Add attribute to Nav Walker in WP (I think it's more a PHP issue)

问题

I'm writing here, because I think it's more PHP related problem, than WordPress.

I've used the menu walker below to display dynamic submenus with great effect in the past. I'm using directly copy&pasted function from wordpress dev page and it was enough to me.

However, now I'm struggling to make a little adjustment to add ID attribute to UL because I'm trying to make dropdowns with MaterializeCSS framework.

I"ve succesfully added ID to match data-activates in anchor data-activates="dropdown1" like this-

<li><a class="dropdown-button" href="#!" data-activates="dropdown1">Dropdown</a></li>

but I can't do the same for UL.

<ul id="dropdown1" class="dropdown-content">

Could you, please, help me with it? Here is material framework documentation http://materializecss.com/navbar.html#navbar-dropdown (in case you would not understand me) and my Naw_walker function

/**
 * 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(
        'dropdown-content',
        ( $display_depth % 2  ? 'menu-odd' : 'menu-even' ),
        ( $display_depth >=2 ? 'sub-sub-menu' : '' ),
        'menu-depth-' . $display_depth
    );
    $class_names = implode( ' ', $classes );

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

    // 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 . '<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="dropdown-button" data-activates="dropdown-'. $item->ID . ( $depth > 0 ? '' : '' ) . '"';
    // $attributes .=  ;



    // Build HTML output and pass through the proper filter.
    $item_output = sprintf( '%1$s<a%2$s>%3$s%4$s%5$s<i class="material-icons right">arrow_drop_down</i></a>%6$s',
        $args->before,
        $attributes,
        $args->link_before,
        apply_filters( 'the_title', $item->title, $item->ID ),
        $args->link_after,
        $args->after
    );

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

}

So Im kindly asking for:
I want to add same ID for UL to match anchors data-activates in order to activate the dropdown menu.

Thanks

回答1:

Well, I've found solution, so I think it would be nice to post it here.

Here's the code which works for me.

    <?php
class Materialize_CSS_Menu_Walker extends Walker {
  var $db_fields = array( 'parent' => 'menu_item_parent', 'id' => 'db_id' );

    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(
            'dropdown-content',
            ( $display_depth % 2  ? 'menu-odd' : 'menu-even' ),
            ( $display_depth >=2 ? 'sub-sub-menu' : '' ),
            'menu-depth-' . $display_depth
        );
        $class_names = implode( ' ', $classes );

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

  function end_lvl( &$output, $depth = 0, $args = array() ) {
    $indent = str_repeat("\t", $depth);
    $output .= "$indent</ul>\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 ) );

        // 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 ) ) );

    /* Add active class */
    if(in_array('current-menu-item', $classes)) {
      $classes[] = 'active';
      unset($classes['current-menu-item']);
    }

    /* Check for children */
    $children = get_posts(array(
      'post_type' => 'nav_menu_item',
      'nopaging' => true,
      'numberposts' => 1,
      'meta_key' => '_menu_item_menu_item_parent',
      'meta_value' => $item->ID
      ));

    if (!empty($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="nav-menu-item-'. $item->ID . '" class="' . $depth_class_names . '">';
    $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 .= ! empty( $children )         ? ' class="dropdown-button" data-activates="dropdown-'. $item->ID .'"' : '';

    $item_output .= '<a'. $attributes .'>';
    $item_output .= $args->link_before . apply_filters( 'the_title', $item->title, $item->ID ) . $args->link_after;

    if(!empty($children))
      $item_output .= '<i class="material-icons right">arrow_drop_down</i>';

    $item_output .= '</a>';

    $item_output .= $args->after;

    if(!empty($children))
      $item_output .= '<ul id="dropdown-'.$item->ID.'"';
    $output .= apply_filters( 'walker_nav_menu_start_el', $item_output, $item, $depth, $args );

  }
  function end_el( &$output, $item, $depth = 0, $args = array() ) {
    $output .= "</li>\n";
  }
}

来源：https://stackoverflow.com/questions/36643900/add-attribute-to-nav-walker-in-wp-i-think-its-more-a-php-issue

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