Post Type Menu "active"

navigation_menu_active.php

add_action('nav_menu_css_class', 'add_current_nav_class', 10, 2 );

function add_current_nav_class($classes, $item) {

	// Getting the current post details
	global $post;

	// Getting the post type of the current post
	$current_post_type = get_post_type_object(get_post_type($post->ID));
	$current_post_type_slug = $current_post_type->rewrite[slug];

	// Getting the URL of the menu item
	$menu_slug = strtolower(trim($item->url));

	// If the menu item URL contains the current post types slug add the current-menu-item class
	if (strpos($menu_slug,$current_post_type_slug) !== false) {

	   $classes[] = 'current-menu-item';

	}

	// Return the corrected set of classes to be added to the menu item
	return $classes;

}