Custom WordPress search form using bootstrap 3.0

gistfile1.phtml

?>
<form class="navbar-form" role="search" action="<?php echo site_url('/'); ?>" method="get" >
        <div class="input-group">
            <input type="text" class="form-control" placeholder="Search" name="s" id="search" value="<?php the_search_query(); ?>">
            <div class="input-group-btn">
                <button class="btn btn-default" type="submit"><i class="glyphicon glyphicon-search"></i></button>
            </div>
        </div>
</form>