[Wordpress] Add a CSS class to nav menu items depending on URL

<?php
/*
From:
http://www.rarescosma.com/2010/11/add-a-class-to-wp_nav_menu-items-with-urls-included-in-the-current-url/
*/

add_filter( 'nav_menu_css_class', 'add_parent_url_menu_class', 10, 2 );

function add_parent_url_menu_class( $classes = array(), $item = false ) {
	// Get current URL
	$current_url = current_url();

	// Get homepage URL
	$homepage_url = trailingslashit( get_bloginfo( 'url' ) );

	// Exclude 404 and homepage
	if( is_404() or $item->url == $homepage_url ) return $classes;

	if ( strstr( $current_url, $item->url) ) {
		// Add the 'parent_url' class
		$classes[] = 'parent_url';
	}

	return $classes;
}

function current_url() {
	// Protocol
	$url = ( 'on' == $_SERVER['HTTPS'] ) ? 'https://' : 'http://';

	$url .= $_SERVER['SERVER_NAME'];

	// Port
	$url .= ( '80' == $_SERVER['SERVER_PORT'] ) ? '' : ':' . $_SERVER['SERVER_PORT'];

	$url .= $_SERVER['REQUEST_URI'];

	return trailingslashit( $url );
}