gistfile1.twig

<script>
    function {{ form_name }}Submit() {
        $.post( '{{ path( form_path ) }}',
                $('#form_{{ form_name }}').serialize(),
                function(data){
                    $('#container_{{ form_name }}').empty().append(data);
                }
        );
        return false;
    }
</script>

<div id="container_{{ form_name }}">
    <form id='form_{{ form_name }}' method="post" {{ form_enctype(form) }} name="{{ form_name }}" >
        {{ form_widget(form) }}
        <input type="button" onclick="{{ form_name }}Submit()" />
    </form>
</div>