collection_widget.twig

{% block collection_widget %}
{% spaceless %}
    <div class="collection">
        {% if prototype is defined %}
            {% set attr = attr|merge({'data-prototype': block('collection_item_widget') }) %}
        {% endif %}
        <div {{ block('widget_container_attributes') }}>
            {{ form_errors(form) }}
            <ul>
            {% for prototype in form %}
                block('collection_item_widget')
            {% endfor %}
            </ul>
            {{ form_rest(form) }}
        </div>
        <div class="clear"></div>
        <a class="add" title="Add" href="javascript:void()">
            <div style="display: none;"></div>
            <span>Add</span>
        </a>
    </div>
    <div class="clear"></div>
{% endspaceless %}
{% endblock collection_widget %}

{% block collection_item_widget %}
{% spaceless %}
    <li>
    {% set fieldNum = 1 %}
    {% for row in prototype %}
        <div class="field{{ fieldNum }}">
        {{ form_label(row) }}
        {{ form_widget(row, { 'attr': { 'class': 'test' }}) }}
        </div>
        {% set fieldNum = fieldNum + 1 %}
    {% endfor %}
        <a class="remove" title="Remove" href="javascript:void()">
            <span>Delete</span>
        </a>
        <div class="clear"></div>
    </li>
{% endspaceless %}
{% endblock collection_item_widget %}

Hey, thx for this !
just to note you have a small typo line 11 :

block('collection_item_widget')

should be :

{{ block('collection_item_widget') }}

I am trying to use collection widget for tag collection in one of the Task/Tag tutorial of Symfony. I am trying to use this in below form for tag collection. I am new to Symfony, and having difficulties getting hold of theme customization. Can you please help me how can I use collection_widget in example form below. Thank You.

<\form action="{{ path('TaskBundle_task') }}" method="POST" {{ form_enctype(form) }}>

{{ form_row(form.title) }}    
{{ form_row(form.description) }}

        <\h3>Tags</h3>
        <ul class="tags" id="tags" data-prototype="{{ form_widget(form.tags.vars.prototype)|e }}">

    {% for tag in form.tags %}
             <li>{{ form_row(tag.name) }} </li>
    {% endfor %}
        </ul>
{{ form_rest(form) }}
        <\input type="submit" value="Submit" />

</form>

Do I need to define javascript:void(). What does it stands for?