Replace wp nav menu links that have just a hash url with headings

nav-menu-headings.php

<?php
/*
Plugin Name: Nav Menu Headings
Plugin URI: https://gist.github.com/mattheu/9093265
Description: Add headings to nav menus
Author: Matth.eu
Version: 0.1-alpha
Author URI: http://matth.eu
Text Domain: nav-menu-headings
Domain Path: /lang
*/

/**
* Replace menu links with a hash url with headings.
*/
add_filter( 'walker_nav_menu_start_el', function( $item_output, $item ) {

	if ( ! isset( $item->url ) || $item->url !== "#" )
		return $item_output;

	$dom = new DOMDocument();
	@$dom->loadHTML( $item_output );

	foreach ( $dom->getElementsByTagName('body')->item(0)->childNodes as $node ) {
		
		if ( '#' !== $node->getAttribute('href') )
			continue;

		// Create new element.
		$new_node = $dom->createElement('h4');
		
		// Copy children.
		while ( $node->childNodes->length > 0 )
			$new_node->appendChild( $node->childNodes->item(0) );

		// Copy attribute
		foreach ( $node->attributes as $attr )
			$new_node->setAttribute( $attr->nodeName, $attr->nodeValue );
		
		// Remove link specific attributes.
		$new_node->removeAttribute( 'href' );
		$new_node->removeAttribute( 'target' );

		// Set a new class
		$new_node->setAttribute( 'class', $new_node->getAttribute( 'class' ) . ' menu-heading' );

		$node->parentNode->replaceChild( $new_node, $node );
		
	}
		
	$r = '';
	foreach ( $dom->getElementsByTagName('body')->item(0)->childNodes as $node )
		$r .= $dom->saveHtml( $node );
		
	return $r;

}, 10, 2 );