add_filter('wp_nav_menu_items','add_search_box', 10, 3); function add_search_box($items, $args) { ob_start(); get_search_form(); $searchform = ob_get_contents(); ob_end_clean(); $items .= '<li class="search_menu"><span class="fa fa-search"></span><ul class="sub-menu"><li class="search_item"></li></ul></li>'; return $items; }