I am having trouble understanding this error and I've not come across it before, please could someone help?
Strict Standards: Declaration of wp_bootstrap_navwalker::start_lvl() should be compatible with Walker_Nav_Menu::start_lvl(&$output, $depth = 0, $args = Array) in .../wp-content/themes/flat-portfolio/wp_bootstrap_navwalker.php on line 143
The wp_bootstrap_navwalker.php code is as follows:
<?php
/**
* Class Name: wp_bootstrap_navwalker
* GitHub URI: https://github.com/twittem/wp-bootstrap-navwalker
* Description: A custom WordPress nav walker class to implement the Twitter Bootstrap 2.3.2 navigation style in a custom theme using the WordPress built in menu manager.
* Version: 1.4.3
* Author: Edward McIntyre - @twittem
* License: GPL-2.0+
* License URI: http://www.gnu.org/licenses/gpl-2.0.txt
*/
class wp_bootstrap_navwalker extends Walker_Nav_Menu {
/**
* @see Walker::start_lvl()
* @since 3.0.0
*
* @param string $output Passed by reference. Used to append additional content.
* @param int $depth Depth of page. Used for padding.
*/
function start_lvl( &$output, $depth ) {
$indent = str_repeat( "\t", $depth );
$output .= "\n$indent<ul class=\"dropdown-menu\">\n";
}
/**
* @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 int $current_page Menu item ID.
* @param object $args
*/
function start_el( &$output, $item, $depth = 0, $args = array(), $id = 0 ) {
global $wp_query;
$indent = ( $depth ) ? str_repeat( "\t", $depth ) : '';
/**
* Dividers & Headers
* ==================
* Determine whether the item is a Divider, Header, or regular menu item.
* To prevent errors we use the strcasecmp() function to so a comparison
* that is not case sensitive. The strcasecmp() function returns a 0 if
* the strings are equal.
*/
if (strcasecmp($item->title, 'divider') == 0) {
// Item is a Divider
$output .= $indent . '<li class="divider">';
} else if (strcasecmp($item->title, 'divider-vertical') == 0) {
// Item is a Vertical Divider
$output .= $indent . '<li class="divider-vertical">';
} else if (strcasecmp($item->title, 'nav-header') == 0) {
// Item is a Header
$output .= $indent . '<li class="nav-header">' . esc_attr( $item->attr_title );
} else {
$class_names = $value = '';
$classes = empty( $item->classes ) ? array() : (array) $item->classes;
$classes[] = ($item->current) ? 'active' : '';
$classes[] = 'menu-item-' . $item->ID;
$class_names = join( ' ', apply_filters( 'nav_menu_css_class', array_filter( $classes ), $item, $args ) );
if ($args->has_children && $depth > 0) {
$class_names .= ' dropdown-submenu';
} else if($args->has_children && $depth === 0) {
$class_names .= ' dropdown';
}
$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 . $value . $class_names .'>';
$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 ) .'"' : '';
$attributes .= ($args->has_children) ? ' data-toggle="dropdown" data-target="#" class="dropdown-toggle"' : '';
$item_output = $args->before;
/**
* Glyphicons
* ===========
* Since the the menu item is NOT a Divider or Header we check the see
* if there is a value in the attr_title property. If the attr_title
* property is NOT null we apply it as the class name for the glyphicon.
*/
if(! empty( $item->attr_title )){
$item_output .= '<a'. $attributes .'><i class="' . esc_attr( $item->attr_title ) . '"></i> ';
} else {
$item_output .= '<a'. $attributes .'>';
}
$item_output .= $args->link_before . apply_filters( 'the_title', $item->title, $item->ID ) . $args->link_after;
$item_output .= ($args->has_children && $depth == 0) ? ' <span class="caret"></span></a>' : '</a>';
$item_output .= $args->after;
$output .= apply_filters( 'walker_nav_menu_start_el', $item_output, $item, $depth, $args );
}
}
/**
* Traverse elements to create list from elements.
*
* Display one element if the element doesn't have any children otherwise,
* display the element and its children. Will only traverse up to the max
* depth and no ignore elements under that depth.
*
* This method shouldn't be called directly, use the walk() method instead.
*
* @see Walker::start_el()
* @since 2.5.0
*
* @param object $element Data object
* @param array $children_elements List of elements to continue traversing.
* @param int $max_depth Max depth to traverse.
* @param int $depth Depth of current element.
* @param array $args
* @param string $output Passed by reference. Used to append additional content.
* @return null Null on failure with no changes to parameters.
*/
function display_element( $element, &$children_elements, $max_depth, $depth, $args, &$output ) {
if ( !$element ) {
return;
}
$id_field = $this->db_fields['id'];
//display this element
if ( is_object( $args[0] ) ) {
$args[0]->has_children = ! empty( $children_elements[$element->$id_field] );
}
parent::display_element($element, $children_elements, $max_depth, $depth, $args, $output);
}
}
?>
I'm calling the walker by putting the following code in my header.php
<?php
wp_nav_menu( array(
'menu' => 'top_menu',
'depth' => 2,
'container' => false,
'menu_class' => 'nav',
'fallback_cb' => 'wp_page_menu',
//Process nav menu using our custom nav walker
'walker' => new wp_bootstrap_navwalker())
);
?>
and registering the function in functions.php:
// Register Custom Navigation Walker
require_once('wp_bootstrap_navwalker.php');
