Add Search Box to Genesis' Primary Menu

functions.php

<?php
// Do NOT include the opening PHP tag

// Add search form to 'primary' menu
function theme_menu_extras( $menu, $args ) {
	// Change 'primary' to 'secondary' to add extras to the secondary navigation menu
	if ( 'primary' !== $args->theme_location )
		return $menu;
	
	// add a search form to the navigation menu
	ob_start();
	get_search_form();
	$search = ob_get_clean();
	$menu  .= '<li class="right search">' . $search . '</li>';
	
	return $menu;
}

add_filter( 'wp_nav_menu_items', 'theme_menu_extras', 10, 2 );