WordPress/wp-includes/nav-menu-template.php
2015-07-07 09:57:26 +00:00

700 lines
25 KiB
PHP

<?php
/**
* Navigation Menu template functions
*
* @package WordPress
* @subpackage Nav_Menus
* @since 3.0.0
*/
/**
* Create HTML list of nav menu items.
*
* @since 3.0.0
* @uses Walker
*/
class Walker_Nav_Menu extends Walker {
/**
* What the class handles.
*
* @see Walker::$tree_type
* @since 3.0.0
* @var string
*/
public $tree_type = array( 'post_type', 'taxonomy', 'custom' );
/**
* Database fields to use.
*
* @see Walker::$db_fields
* @since 3.0.0
* @todo Decouple this.
* @var array
*/
public $db_fields = array( 'parent' => 'menu_item_parent', 'id' => 'db_id' );
/**
* Starts the list before the elements are added.
*
* @see Walker::start_lvl()
*
* @since 3.0.0
*
* @param string $output Passed by reference. Used to append additional content.
* @param int $depth Depth of menu item. Used for padding.
* @param array $args An array of arguments. @see wp_nav_menu()
*/
public function start_lvl( &$output, $depth = 0, $args = array() ) {
$indent = str_repeat("\t", $depth);
$output .= "\n$indent<ul class=\"sub-menu\">\n";
}
/**
* Ends the list of after the elements are added.
*
* @see Walker::end_lvl()
*
* @since 3.0.0
*
* @param string $output Passed by reference. Used to append additional content.
* @param int $depth Depth of menu item. Used for padding.
* @param array $args An array of arguments. @see wp_nav_menu()
*/
public function end_lvl( &$output, $depth = 0, $args = array() ) {
$indent = str_repeat("\t", $depth);
$output .= "$indent</ul>\n";
}
/**
* Start the element output.
*
* @see Walker::start_el()
*
* @since 3.0.0
*
* @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 $id Current item ID.
*/
public function start_el( &$output, $item, $depth = 0, $args = array(), $id = 0 ) {
$indent = ( $depth ) ? str_repeat( "\t", $depth ) : '';
$classes = empty( $item->classes ) ? array() : (array) $item->classes;
$classes[] = 'menu-item-' . $item->ID;
/**
* Filter the CSS class(es) applied to a menu item's list item element.
*
* @since 3.0.0
* @since 4.1.0 The `$depth` parameter was added.
*
* @param array $classes The CSS classes that are applied to the menu item's `<li>` element.
* @param object $item The current menu item.
* @param array $args An array of {@see wp_nav_menu()} arguments.
* @param int $depth Depth of menu item. Used for padding.
*/
$class_names = join( ' ', apply_filters( 'nav_menu_css_class', array_filter( $classes ), $item, $args, $depth ) );
$class_names = $class_names ? ' class="' . esc_attr( $class_names ) . '"' : '';
/**
* Filter the ID applied to a menu item's list item element.
*
* @since 3.0.1
* @since 4.1.0 The `$depth` parameter was added.
*
* @param string $menu_id The ID that is applied to the menu item's `<li>` element.
* @param object $item The current menu item.
* @param array $args An array of {@see wp_nav_menu()} arguments.
* @param int $depth Depth of menu item. Used for padding.
*/
$id = apply_filters( 'nav_menu_item_id', 'menu-item-'. $item->ID, $item, $args, $depth );
$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 ) ? $item->url : '';
/**
* Filter the HTML attributes applied to a menu item's anchor element.
*
* @since 3.6.0
* @since 4.1.0 The `$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.
* }
* @param object $item The current menu item.
* @param array $args An array of {@see 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 ( ! empty( $value ) ) {
$value = ( 'href' === $attr ) ? esc_url( $value ) : esc_attr( $value );
$attributes .= ' ' . $attr . '="' . $value . '"';
}
}
$item_output = $args->before;
$item_output .= '<a'. $attributes .'>';
/** This filter is documented in wp-includes/post-template.php */
$item_output .= $args->link_before . apply_filters( 'the_title', $item->title, $item->ID ) . $args->link_after;
$item_output .= '</a>';
$item_output .= $args->after;
/**
* Filter a menu item's starting output.
*
* The menu item's starting output only includes `$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 object $item Menu item data object.
* @param int $depth Depth of menu item. Used for padding.
* @param array $args An array of {@see wp_nav_menu()} arguments.
*/
$output .= apply_filters( 'walker_nav_menu_start_el', $item_output, $item, $depth, $args );
}
/**
* Ends the element output, if needed.
*
* @see Walker::end_el()
*
* @since 3.0.0
*
* @param string $output Passed by reference. Used to append additional content.
* @param object $item Page data object. Not used.
* @param int $depth Depth of page. Not Used.
* @param array $args An array of arguments. @see wp_nav_menu()
*/
public function end_el( &$output, $item, $depth = 0, $args = array() ) {
$output .= "</li>\n";
}
} // Walker_Nav_Menu
/**
* Displays a navigation menu.
*
* @since 3.0.0
*
* @staticvar array $menu_id_slugs
*
* @param array $args {
* Optional. Array of nav menu arguments.
*
* @type string $menu Desired menu. Accepts (matching in order) id, slug, name. Default empty.
* @type string $menu_class CSS class to use for the ul element which forms the menu. Default 'menu'.
* @type string $menu_id The ID that is applied to the ul element which forms the menu.
* Default is the menu slug, incremented.
* @type string $container Whether to wrap the ul, and what to wrap it with. Default 'div'.
* @type string $container_class Class that is applied to the container. Default 'menu-{menu slug}-container'.
* @type string $container_id The ID that is applied to the container. Default empty.
* @type callback|bool $fallback_cb If the menu doesn't exists, a callback function will fire.
* Default is 'wp_page_menu'. Set to false for no fallback.
* @type string $before Text before the link text. Default empty.
* @type string $after Text after the link text. Default empty.
* @type string $link_before Text before the link. Default empty.
* @type string $link_after Text after the link. Default empty.
* @type bool $echo Whether to echo the menu or return it. Default true.
* @type int $depth How many levels of the hierarchy are to be included. 0 means all. Default 0.
* @type object $walker Instance of a custom walker class. Default empty.
* @type string $theme_location Theme location to be used. Must be registered with register_nav_menu()
* in order to be selectable by the user.
* @type string $items_wrap How the list items should be wrapped. Default is a ul with an id and class.
* Uses printf() format with numbered placeholders.
* }
* @return object|false|void Menu output if $echo is false, false if there are no items or no menu was found.
*/
function wp_nav_menu( $args = array() ) {
static $menu_id_slugs = array();
$defaults = array( 'menu' => '', 'container' => 'div', 'container_class' => '', 'container_id' => '', 'menu_class' => 'menu', 'menu_id' => '',
'echo' => true, 'fallback_cb' => 'wp_page_menu', 'before' => '', 'after' => '', 'link_before' => '', 'link_after' => '', 'items_wrap' => '<ul id="%1$s" class="%2$s">%3$s</ul>',
'depth' => 0, 'walker' => '', 'theme_location' => '' );
// Prevent a fallback_cb in Customizer Preview to assist with has_nav_menu() and partial refresh.
if ( is_customize_preview() ) {
$defaults['fallback_cb'] = '';
}
$args = wp_parse_args( $args, $defaults );
/**
* Filter the arguments used to display a navigation menu.
*
* @since 3.0.0
*
* @see wp_nav_menu()
*
* @param array $args Array of wp_nav_menu() arguments.
*/
$args = apply_filters( 'wp_nav_menu_args', $args );
$args = (object) $args;
/**
* Filter whether to short-circuit the wp_nav_menu() output.
*
* Returning a non-null value to the filter will short-circuit
* wp_nav_menu(), echoing that value if $args->echo is true,
* returning that value otherwise.
*
* @since 3.9.0
*
* @see wp_nav_menu()
*
* @param string|null $output Nav menu output to short-circuit with. Default null.
* @param object $args An object containing wp_nav_menu() arguments.
*/
$nav_menu = apply_filters( 'pre_wp_nav_menu', null, $args );
if ( null !== $nav_menu ) {
if ( $args->echo ) {
echo $nav_menu;
return;
}
return $nav_menu;
}
// Get the nav menu based on the requested menu
$menu = wp_get_nav_menu_object( $args->menu );
// Get the nav menu based on the theme_location
if ( ! $menu && $args->theme_location && ( $locations = get_nav_menu_locations() ) && isset( $locations[ $args->theme_location ] ) )
$menu = wp_get_nav_menu_object( $locations[ $args->theme_location ] );
// get the first menu that has items if we still can't find a menu
if ( ! $menu && !$args->theme_location ) {
$menus = wp_get_nav_menus();
foreach ( $menus as $menu_maybe ) {
if ( $menu_items = wp_get_nav_menu_items( $menu_maybe->term_id, array( 'update_post_term_cache' => false ) ) ) {
$menu = $menu_maybe;
break;
}
}
}
if ( empty( $args->menu ) ) {
$args->menu = $menu;
}
// If the menu exists, get its items.
if ( $menu && ! is_wp_error($menu) && !isset($menu_items) )
$menu_items = wp_get_nav_menu_items( $menu->term_id, array( 'update_post_term_cache' => false ) );
/*
* If no menu was found:
* - Fall back (if one was specified), or bail.
*
* If no menu items were found:
* - Fall back, but only if no theme location was specified.
* - Otherwise, bail.
*/
if ( ( !$menu || is_wp_error($menu) || ( isset($menu_items) && empty($menu_items) && !$args->theme_location ) )
&& isset( $args->fallback_cb ) && $args->fallback_cb && is_callable( $args->fallback_cb ) )
return call_user_func( $args->fallback_cb, (array) $args );
if ( ! $menu || is_wp_error( $menu ) )
return false;
$nav_menu = $items = '';
$show_container = false;
if ( $args->container ) {
/**
* Filter the list of HTML tags that are valid for use as menu containers.
*
* @since 3.0.0
*
* @param array $tags The acceptable HTML tags for use as menu containers.
* Default is array containing 'div' and 'nav'.
*/
$allowed_tags = apply_filters( 'wp_nav_menu_container_allowedtags', array( 'div', 'nav' ) );
if ( in_array( $args->container, $allowed_tags ) ) {
$show_container = true;
$class = $args->container_class ? ' class="' . esc_attr( $args->container_class ) . '"' : ' class="menu-'. $menu->slug .'-container"';
$id = $args->container_id ? ' id="' . esc_attr( $args->container_id ) . '"' : '';
$nav_menu .= '<'. $args->container . $id . $class . '>';
}
}
// Set up the $menu_item variables
_wp_menu_item_classes_by_context( $menu_items );
$sorted_menu_items = $menu_items_with_children = array();
foreach ( (array) $menu_items as $menu_item ) {
$sorted_menu_items[ $menu_item->menu_order ] = $menu_item;
if ( $menu_item->menu_item_parent )
$menu_items_with_children[ $menu_item->menu_item_parent ] = true;
}
// Add the menu-item-has-children class where applicable
if ( $menu_items_with_children ) {
foreach ( $sorted_menu_items as &$menu_item ) {
if ( isset( $menu_items_with_children[ $menu_item->ID ] ) )
$menu_item->classes[] = 'menu-item-has-children';
}
}
unset( $menu_items, $menu_item );
/**
* Filter the sorted list of menu item objects before generating the menu's HTML.
*
* @since 3.1.0
*
* @param array $sorted_menu_items The menu items, sorted by each menu item's menu order.
* @param object $args An object containing wp_nav_menu() arguments.
*/
$sorted_menu_items = apply_filters( 'wp_nav_menu_objects', $sorted_menu_items, $args );
$items .= walk_nav_menu_tree( $sorted_menu_items, $args->depth, $args );
unset($sorted_menu_items);
// Attributes
if ( ! empty( $args->menu_id ) ) {
$wrap_id = $args->menu_id;
} else {
$wrap_id = 'menu-' . $menu->slug;
while ( in_array( $wrap_id, $menu_id_slugs ) ) {
if ( preg_match( '#-(\d+)$#', $wrap_id, $matches ) )
$wrap_id = preg_replace('#-(\d+)$#', '-' . ++$matches[1], $wrap_id );
else
$wrap_id = $wrap_id . '-1';
}
}
$menu_id_slugs[] = $wrap_id;
$wrap_class = $args->menu_class ? $args->menu_class : '';
/**
* Filter the HTML list content for navigation menus.
*
* @since 3.0.0
*
* @see wp_nav_menu()
*
* @param string $items The HTML list content for the menu items.
* @param object $args An object containing wp_nav_menu() arguments.
*/
$items = apply_filters( 'wp_nav_menu_items', $items, $args );
/**
* Filter the HTML list content for a specific navigation menu.
*
* @since 3.0.0
*
* @see wp_nav_menu()
*
* @param string $items The HTML list content for the menu items.
* @param object $args An object containing wp_nav_menu() arguments.
*/
$items = apply_filters( "wp_nav_menu_{$menu->slug}_items", $items, $args );
// Don't print any markup if there are no items at this point.
if ( empty( $items ) )
return false;
$nav_menu .= sprintf( $args->items_wrap, esc_attr( $wrap_id ), esc_attr( $wrap_class ), $items );
unset( $items );
if ( $show_container )
$nav_menu .= '</' . $args->container . '>';
/**
* Filter the HTML content for navigation menus.
*
* @since 3.0.0
*
* @see wp_nav_menu()
*
* @param string $nav_menu The HTML content for the navigation menu.
* @param object $args An object containing wp_nav_menu() arguments.
*/
$nav_menu = apply_filters( 'wp_nav_menu', $nav_menu, $args );
if ( $args->echo )
echo $nav_menu;
else
return $nav_menu;
}
/**
* Add the class property classes for the current context, if applicable.
*
* @access private
* @since 3.0.0
*
* @global WP_Query $wp_query
* @global WP_Rewrite $wp_rewrite
*
* @param array $menu_items The current menu item objects to which to add the class property information.
*/
function _wp_menu_item_classes_by_context( &$menu_items ) {
global $wp_query, $wp_rewrite;
$queried_object = $wp_query->get_queried_object();
$queried_object_id = (int) $wp_query->queried_object_id;
$active_object = '';
$active_ancestor_item_ids = array();
$active_parent_item_ids = array();
$active_parent_object_ids = array();
$possible_taxonomy_ancestors = array();
$possible_object_parents = array();
$home_page_id = (int) get_option( 'page_for_posts' );
if ( $wp_query->is_singular && ! empty( $queried_object->post_type ) && ! is_post_type_hierarchical( $queried_object->post_type ) ) {
foreach ( (array) get_object_taxonomies( $queried_object->post_type ) as $taxonomy ) {
if ( is_taxonomy_hierarchical( $taxonomy ) ) {
$term_hierarchy = _get_term_hierarchy( $taxonomy );
$terms = wp_get_object_terms( $queried_object_id, $taxonomy, array( 'fields' => 'ids' ) );
if ( is_array( $terms ) ) {
$possible_object_parents = array_merge( $possible_object_parents, $terms );
$term_to_ancestor = array();
foreach ( (array) $term_hierarchy as $anc => $descs ) {
foreach ( (array) $descs as $desc )
$term_to_ancestor[ $desc ] = $anc;
}
foreach ( $terms as $desc ) {
do {
$possible_taxonomy_ancestors[ $taxonomy ][] = $desc;
if ( isset( $term_to_ancestor[ $desc ] ) ) {
$_desc = $term_to_ancestor[ $desc ];
unset( $term_to_ancestor[ $desc ] );
$desc = $_desc;
} else {
$desc = 0;
}
} while ( ! empty( $desc ) );
}
}
}
}
} elseif ( ! empty( $queried_object->taxonomy ) && is_taxonomy_hierarchical( $queried_object->taxonomy ) ) {
$term_hierarchy = _get_term_hierarchy( $queried_object->taxonomy );
$term_to_ancestor = array();
foreach ( (array) $term_hierarchy as $anc => $descs ) {
foreach ( (array) $descs as $desc )
$term_to_ancestor[ $desc ] = $anc;
}
$desc = $queried_object->term_id;
do {
$possible_taxonomy_ancestors[ $queried_object->taxonomy ][] = $desc;
if ( isset( $term_to_ancestor[ $desc ] ) ) {
$_desc = $term_to_ancestor[ $desc ];
unset( $term_to_ancestor[ $desc ] );
$desc = $_desc;
} else {
$desc = 0;
}
} while ( ! empty( $desc ) );
}
$possible_object_parents = array_filter( $possible_object_parents );
$front_page_url = home_url();
foreach ( (array) $menu_items as $key => $menu_item ) {
$menu_items[$key]->current = false;
$classes = (array) $menu_item->classes;
$classes[] = 'menu-item';
$classes[] = 'menu-item-type-' . $menu_item->type;
$classes[] = 'menu-item-object-' . $menu_item->object;
// if the menu item corresponds to a taxonomy term for the currently-queried non-hierarchical post object
if ( $wp_query->is_singular && 'taxonomy' == $menu_item->type && in_array( $menu_item->object_id, $possible_object_parents ) ) {
$active_parent_object_ids[] = (int) $menu_item->object_id;
$active_parent_item_ids[] = (int) $menu_item->db_id;
$active_object = $queried_object->post_type;
// if the menu item corresponds to the currently-queried post or taxonomy object
} elseif (
$menu_item->object_id == $queried_object_id &&
(
( ! empty( $home_page_id ) && 'post_type' == $menu_item->type && $wp_query->is_home && $home_page_id == $menu_item->object_id ) ||
( 'post_type' == $menu_item->type && $wp_query->is_singular ) ||
( 'taxonomy' == $menu_item->type && ( $wp_query->is_category || $wp_query->is_tag || $wp_query->is_tax ) && $queried_object->taxonomy == $menu_item->object )
)
) {
$classes[] = 'current-menu-item';
$menu_items[$key]->current = true;
$_anc_id = (int) $menu_item->db_id;
while(
( $_anc_id = get_post_meta( $_anc_id, '_menu_item_menu_item_parent', true ) ) &&
! in_array( $_anc_id, $active_ancestor_item_ids )
) {
$active_ancestor_item_ids[] = $_anc_id;
}
if ( 'post_type' == $menu_item->type && 'page' == $menu_item->object ) {
// Back compat classes for pages to match wp_page_menu()
$classes[] = 'page_item';
$classes[] = 'page-item-' . $menu_item->object_id;
$classes[] = 'current_page_item';
}
$active_parent_item_ids[] = (int) $menu_item->menu_item_parent;
$active_parent_object_ids[] = (int) $menu_item->post_parent;
$active_object = $menu_item->object;
// if the menu item corresponds to the currently-requested URL
} elseif ( 'custom' == $menu_item->object ) {
$_root_relative_current = untrailingslashit( $_SERVER['REQUEST_URI'] );
$current_url = set_url_scheme( 'http://' . $_SERVER['HTTP_HOST'] . $_root_relative_current );
$raw_item_url = strpos( $menu_item->url, '#' ) ? substr( $menu_item->url, 0, strpos( $menu_item->url, '#' ) ) : $menu_item->url;
$item_url = set_url_scheme( untrailingslashit( $raw_item_url ) );
$_indexless_current = untrailingslashit( preg_replace( '/' . preg_quote( $wp_rewrite->index, '/' ) . '$/', '', $current_url ) );
if ( $raw_item_url && in_array( $item_url, array( $current_url, $_indexless_current, $_root_relative_current ) ) ) {
$classes[] = 'current-menu-item';
$menu_items[$key]->current = true;
$_anc_id = (int) $menu_item->db_id;
while(
( $_anc_id = get_post_meta( $_anc_id, '_menu_item_menu_item_parent', true ) ) &&
! in_array( $_anc_id, $active_ancestor_item_ids )
) {
$active_ancestor_item_ids[] = $_anc_id;
}
if ( in_array( home_url(), array( untrailingslashit( $current_url ), untrailingslashit( $_indexless_current ) ) ) ) {
// Back compat for home link to match wp_page_menu()
$classes[] = 'current_page_item';
}
$active_parent_item_ids[] = (int) $menu_item->menu_item_parent;
$active_parent_object_ids[] = (int) $menu_item->post_parent;
$active_object = $menu_item->object;
// give front page item current-menu-item class when extra query arguments involved
} elseif ( $item_url == $front_page_url && is_front_page() ) {
$classes[] = 'current-menu-item';
}
if ( untrailingslashit($item_url) == home_url() )
$classes[] = 'menu-item-home';
}
// back-compat with wp_page_menu: add "current_page_parent" to static home page link for any non-page query
if ( ! empty( $home_page_id ) && 'post_type' == $menu_item->type && empty( $wp_query->is_page ) && $home_page_id == $menu_item->object_id )
$classes[] = 'current_page_parent';
$menu_items[$key]->classes = array_unique( $classes );
}
$active_ancestor_item_ids = array_filter( array_unique( $active_ancestor_item_ids ) );
$active_parent_item_ids = array_filter( array_unique( $active_parent_item_ids ) );
$active_parent_object_ids = array_filter( array_unique( $active_parent_object_ids ) );
// set parent's class
foreach ( (array) $menu_items as $key => $parent_item ) {
$classes = (array) $parent_item->classes;
$menu_items[$key]->current_item_ancestor = false;
$menu_items[$key]->current_item_parent = false;
if (
isset( $parent_item->type ) &&
(
// ancestral post object
(
'post_type' == $parent_item->type &&
! empty( $queried_object->post_type ) &&
is_post_type_hierarchical( $queried_object->post_type ) &&
in_array( $parent_item->object_id, $queried_object->ancestors ) &&
$parent_item->object != $queried_object->ID
) ||
// ancestral term
(
'taxonomy' == $parent_item->type &&
isset( $possible_taxonomy_ancestors[ $parent_item->object ] ) &&
in_array( $parent_item->object_id, $possible_taxonomy_ancestors[ $parent_item->object ] ) &&
(
! isset( $queried_object->term_id ) ||
$parent_item->object_id != $queried_object->term_id
)
)
)
) {
$classes[] = empty( $queried_object->taxonomy ) ? 'current-' . $queried_object->post_type . '-ancestor' : 'current-' . $queried_object->taxonomy . '-ancestor';
}
if ( in_array( intval( $parent_item->db_id ), $active_ancestor_item_ids ) ) {
$classes[] = 'current-menu-ancestor';
$menu_items[$key]->current_item_ancestor = true;
}
if ( in_array( $parent_item->db_id, $active_parent_item_ids ) ) {
$classes[] = 'current-menu-parent';
$menu_items[$key]->current_item_parent = true;
}
if ( in_array( $parent_item->object_id, $active_parent_object_ids ) )
$classes[] = 'current-' . $active_object . '-parent';
if ( 'post_type' == $parent_item->type && 'page' == $parent_item->object ) {
// Back compat classes for pages to match wp_page_menu()
if ( in_array('current-menu-parent', $classes) )
$classes[] = 'current_page_parent';
if ( in_array('current-menu-ancestor', $classes) )
$classes[] = 'current_page_ancestor';
}
$menu_items[$key]->classes = array_unique( $classes );
}
}
/**
* Retrieve the HTML list content for nav menu items.
*
* @uses Walker_Nav_Menu to create HTML list content.
* @since 3.0.0
*
* @param array $items
* @param int $depth
* @param object $r
* @return string
*/
function walk_nav_menu_tree( $items, $depth, $r ) {
$walker = ( empty($r->walker) ) ? new Walker_Nav_Menu : $r->walker;
$args = array( $items, $depth, $r );
return call_user_func_array( array( $walker, 'walk' ), $args );
}
/**
* Prevents a menu item ID from being used more than once.
*
* @since 3.0.1
* @access private
*
* @staticvar array $used_ids
* @param string $id
* @param object $item
* @return string
*/
function _nav_menu_item_id_use_once( $id, $item ) {
static $_used_ids = array();
if ( in_array( $item->ID, $_used_ids ) ) {
return '';
}
$_used_ids[] = $item->ID;
return $id;
}