function navigation()
{
	wp_nav_menu(
	array(
		'theme_location'  => 'header-menu',
		'menu'            => '',
		'container'       => 'ul',
		'container_class' => 'menu-{menu slug}-container',
		'container_class' => '',
		'container_id'    => '',
		'menu_class'      => '',
		'menu_id'         => '',
		'echo'            => false,
		'fallback_cb'     => 'wp_page_menu',
		'before'          => '',
		'after'           => '',
		'link_before'     => '',
		'link_after'      => '',
		'items_wrap'      => '%3$s',
		'depth'           => 0,
		'walker'          => '',
		)
	);
}

function register_navigation()
{
    register_nav_menus(array(
        'header-menu' => __('Nagłówek', 'navigation'),
        'footer-menu' => __('Stopka', 'navigation')
    ));
}
add_action('init', 'register_navigation');

	function clean_custom_menus() {
		$menu_name = 'navigation';
		if (($locations = get_nav_menu_locations()) && isset($locations[$menu_name])) {
			$menu = wp_get_nav_menu_object($locations[$menu_name]);
			$menu_items = wp_get_nav_menu_items($menu->term_id);

			$menu_list = '<nav>' ."\n";
			$menu_list .= "\t\t\t\t". '<ul>' ."\n";
			foreach ((array) $menu_items as $key => $menu_item) {
				$title = $menu_item->title;
				$url = $menu_item->url;
				$menu_list .= "\t\t\t\t\t". '<li><a href="'. $url .'">'. $title .'</a></li>' ."\n";
			}
			$menu_list .= "\t\t\t\t". '</ul>' ."\n";
			$menu_list .= "\t\t\t". '</nav>' ."\n";
		}
		echo $menu_list;
	}

	function wp_nav_menu_attributes_filter($var) {
		return is_array($var) ? array_intersect($var, array('current-menu-item')) : '';
	}

	add_filter('nav_menu_css_class', 'wp_nav_menu_attributes_filter', 100, 1);
	add_filter('nav_menu_item_id', 'wp_nav_menu_attributes_filter', 100, 1);
	add_filter('page_css_class', 'wp_nav_menu_attributes_filter', 100, 1);