Wordpress: How to add a search bar to the main menu

Add the following code into function.php file:

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

function add_search_box($items, $args) {

    if($args->theme_location == 'header-menu') {

        ob_start();

        get_search_form();

        $searchform = ob_get_contents();

        ob_end_clean();

 

        return $items .= '<li id="searchform-item">' . $searchform . '</li>';

    }

    return $items;

}

add the following in the style.css file:

#searchform{

    margin:7px;

}

#searchform-item input[type="text"] {

    width: auto;

}

#searchform-item {

    float: right;

}