{{ use('yii/widgets/ActiveForm') }}

{% set form = active_form_begin({
    'id': 'login-form',
    'action' : '/form-handler',
    'options': {
        'class': 'form-horizontal',
    }
}) %}
    {{ form.field(model, 'firstName') | raw }}
    <div class="form-group">
        <div class="col-lg-offset-1 col-lg-11">
            {{ html.submitButton('Login', {
                'class': 'btn btn-primary',
            }) | raw }}
        </div>
    </div>
{{ active_form_end() }}