Example of Walker_Nav_Menu class extension, to create your own custom HTML code which is outputs by function wp_nav_menu(). Our HTML code will be written specifically for our theme.
Below is the code of its own arbitrary class that builds the menu. It adds menu depth and even/odd CSS classes to menu elements (both ul and li):
To avoid reinventing the wheel, we copy the code of the Walker_Nav_Menu{} class and just modify it as we need.
class Walker_Nav_Menu extends Walker {
/**
* What the class handles.
*
* @since 3.0.0
* @var string
*
* @see Walker::$tree_type
*/
public $tree_type = array( 'post_type', 'taxonomy', 'custom' );
/**
* Database fields to use.
*
* @since 3.0.0
* @todo Decouple this.
* @var string[]
*
* @see Walker::$db_fields
*/
public $db_fields = array(
'parent' => 'menu_item_parent',
'id' => 'db_id',
);
/**
* Starts the list before the elements are added.
*
* @since 3.0.0
*
* @see Walker::start_lvl()
*
* @param string $output Used to append additional content (passed by reference).
* @param int $depth Depth of menu item. Used for padding.
* @param stdClass $args An object of wp_nav_menu() arguments.
*/
public function start_lvl( &$output, $depth = 0, $args = null ) {
if ( isset( $args->item_spacing ) && 'discard' === $args->item_spacing ) {
$t = '';
$n = '';
} else {
$t = "\t";
$n = "\n";
}
$indent = str_repeat( $t, $depth );
// Default class.
$classes = array( 'sub-menu' );
/**
* Filters the CSS class(es) applied to a menu list element.
*
* @since 4.8.0
*
* @param string[] $classes Array of the CSS classes that are applied to the menu `<ul>` element.
* @param stdClass $args An object of `wp_nav_menu()` arguments.
* @param int $depth Depth of menu item. Used for padding.
*/
$class_names = implode( ' ', apply_filters( 'nav_menu_submenu_css_class', $classes, $args, $depth ) );
$atts = array();
$atts['class'] = ! empty( $class_names ) ? $class_names : '';
/**
* Filters the HTML attributes applied to a menu list element.
*
* @since 6.3.0
*
* @param array $atts {
* The HTML attributes applied to the `<ul>` element, empty strings are ignored.
*
* @type string $class HTML CSS class attribute.
* }
* @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_submenu_attributes', $atts, $args, $depth );
$attributes = $this->build_atts( $atts );
$output .= "{$n}{$indent}<ul{$attributes}>{$n}";
}
/**
* Ends the list of after the elements are added.
*
* @since 3.0.0
*
* @see Walker::end_lvl()
*
* @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";
}
$indent = str_repeat( $t, $depth );
$output .= "$indent</ul>{$n}";
}
/**
* Starts the element output.
*
* @since 3.0.0
* @since 4.4.0 The {@see 'nav_menu_item_args'} filter was added.
* @since 5.9.0 Renamed `$item` to `$data_object` and `$id` to `$current_object_id`
* to match parent class for PHP 8 named parameter support.
*
* @see Walker::start_el()
*
* @param string $output Used to append additional content (passed by reference).
* @param WP_Post $data_object Menu item data object.
* @param int $depth Depth of menu item. Used for padding.
* @param stdClass $args An object of wp_nav_menu() arguments.
* @param int $current_object_id Optional. ID of the current menu item. Default 0.
*/
public function start_el( &$output, $data_object, $depth = 0, $args = null, $current_object_id = 0 ) {
// Restores the more descriptive, specific name for use within this method.
$menu_item = $data_object;
if ( isset( $args->item_spacing ) && 'discard' === $args->item_spacing ) {
$t = '';
$n = '';
} else {
$t = "\t";
$n = "\n";
}
$indent = ( $depth ) ? str_repeat( $t, $depth ) : '';
$classes = empty( $menu_item->classes ) ? array() : (array) $menu_item->classes;
$classes[] = 'menu-item-' . $menu_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 $menu_item Menu item data object.
* @param int $depth Depth of menu item. Used for padding.
*/
$args = apply_filters( 'nav_menu_item_args', $args, $menu_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 $menu_item The current menu item object.
* @param stdClass $args An object of wp_nav_menu() arguments.
* @param int $depth Depth of menu item. Used for padding.
*/
$class_names = implode( ' ', apply_filters( 'nav_menu_css_class', array_filter( $classes ), $menu_item, $args, $depth ) );
/**
* Filters the ID attribute applied to a menu item's list item element.
*
* @since 3.0.1
* @since 4.1.0 The `$depth` parameter was added.
*
* @param string $menu_item_id The ID attribute applied to the menu item's `<li>` element.
* @param WP_Post $menu_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.
*/
$id = apply_filters( 'nav_menu_item_id', 'menu-item-' . $menu_item->ID, $menu_item, $args, $depth );
$li_atts = array();
$li_atts['id'] = ! empty( $id ) ? $id : '';
$li_atts['class'] = ! empty( $class_names ) ? $class_names : '';
/**
* Filters the HTML attributes applied to a menu's list item element.
*
* @since 6.3.0
*
* @param array $li_atts {
* The HTML attributes applied to the menu item's `<li>` element, empty strings are ignored.
*
* @type string $class HTML CSS class attribute.
* @type string $id HTML id attribute.
* }
* @param WP_Post $menu_item The current menu item object.
* @param stdClass $args An object of wp_nav_menu() arguments.
* @param int $depth Depth of menu item. Used for padding.
*/
$li_atts = apply_filters( 'nav_menu_item_attributes', $li_atts, $menu_item, $args, $depth );
$li_attributes = $this->build_atts( $li_atts );
$output .= $indent . '<li' . $li_attributes . '>';
$atts = array();
$atts['title'] = ! empty( $menu_item->attr_title ) ? $menu_item->attr_title : '';
$atts['target'] = ! empty( $menu_item->target ) ? $menu_item->target : '';
if ( '_blank' === $menu_item->target && empty( $menu_item->xfn ) ) {
$atts['rel'] = 'noopener';
} else {
$atts['rel'] = $menu_item->xfn;
}
if ( ! empty( $menu_item->url ) ) {
if ( get_privacy_policy_url() === $menu_item->url ) {
$atts['rel'] = empty( $atts['rel'] ) ? 'privacy-policy' : $atts['rel'] . ' privacy-policy';
}
$atts['href'] = $menu_item->url;
} else {
$atts['href'] = '';
}
$atts['aria-current'] = $menu_item->current ? 'page' : '';
/**
* Filters the HTML attributes applied to a menu item's anchor element.
*
* @since 3.6.0
* @since 4.1.0 The `$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 $menu_item The current menu item object.
* @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, $menu_item, $args, $depth );
$attributes = $this->build_atts( $atts );
/** This filter is documented in wp-includes/post-template.php */
$title = apply_filters( 'the_title', $menu_item->title, $menu_item->ID );
/**
* Filters a menu item's title.
*
* @since 4.4.0
*
* @param string $title The menu item's title.
* @param WP_Post $menu_item The current menu item object.
* @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, $menu_item, $args, $depth );
$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 $menu_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, $menu_item, $depth, $args );
}
/**
* Ends the element output, if needed.
*
* @since 3.0.0
* @since 5.9.0 Renamed `$item` to `$data_object` to match parent class for PHP 8 named parameter support.
*
* @see Walker::end_el()
*
* @param string $output Used to append additional content (passed by reference).
* @param WP_Post $data_object Menu item data object. Not used.
* @param int $depth Depth of page. Not Used.
* @param stdClass $args An object of wp_nav_menu() arguments.
*/
public function end_el( &$output, $data_object, $depth = 0, $args = null ) {
if ( isset( $args->item_spacing ) && 'discard' === $args->item_spacing ) {
$t = '';
$n = '';
} else {
$t = "\t";
$n = "\n";
}
$output .= "</li>{$n}";
}
/**
* Builds a string of HTML attributes from an array of key/value pairs.
* Empty values are ignored.
*
* @since 6.3.0
*
* @param array $atts Optional. An array of HTML attribute key/value pairs. Default empty array.
* @return string A string of HTML attributes.
*/
protected function build_atts( $atts = array() ) {
$attribute_string = '';
foreach ( $atts as $attr => $value ) {
if ( false !== $value && '' !== $value && is_scalar( $value ) ) {
$value = ( 'href' === $attr ) ? esc_url( $value ) : esc_attr( $value );
$attribute_string .= ' ' . $attr . '="' . $value . '"';
}
}
return $attribute_string;
}
}