// Menu items and corresponding category IDs
		$menu_items_to_categorise = array(10 => 1, 11 => 2, 12 => 3);

		// Get current URL
		$current_url = (isset($_SERVER['HTTPS']) ? 'https' : 'http') . '://' . $_SERVER['HTTP_HOST'] . $_SERVER['REQUEST_URI'];

		// Get the WordPress generated menu
		$nav_menu = wp_nav_menu( array( 'container_class' => 'menu-header', 'theme_location' => 'primary', 'echo' => 0 ) );

		// Loop through the items to categorise
		foreach ($menu_items_to_categorise as $menu_item_number => $menu_item_cat) {

			// Get the posts for the current menu-item number
			global $post;
			$tmp_post = $post;
			$args = array( 'category' => $menu_item_cat );
			$myposts = get_posts( $args );

			// Create list
			$posts_sub_menu = "\n" . '<ul class="sub-menu">' . "\n";

			// Loop through the posts and append the list entries
			foreach( $myposts as $post ) :
				setup_postdata($post);
				$posts_sub_menu .= '<li class="menu-item menu-item-type-custom menu-item-object-custom' . (get_permalink() == $current_url ? ' current-menu-item' : '' ) . '"><a href="'. get_permalink() . '">' . get_the_title() . "</a></li>\n";
			endforeach;
			$posts_sub_menu .= "</ul>\n";

			// Return to the parent loop so there will be no conflict
			$post = $tmp_post;

			// Inject created list into existing menu
			$pattern = "%(<li [^>]*id=\"menu-item-" . $menu_item_number . "\"[^>]*>.*)(</li>)%mU";
			$replacement = '${1}' . $posts_sub_menu . '$2';
			$nav_menu = preg_replace($pattern, $replacement, $nav_menu);
		}
		unset($menu_item_number);
		unset($menu_item_cat);