tp5-form-builder/view/public/items/checkbox.html

<div class="form-group col-lg-12 col-md-12 col-sm-12 col-xs-12" id="form_group_{$form.name}">
    <div class="col-xs-12 label-title" for="{$form.name}" style="margin-bottom: 14px;">{$form.title|htmlspecialchars}</div>
    <div class="col-xs-12">
        {volist name="form.extra" id="option"}
        <label class="pr10">
            <input type="checkbox" data-toggle="icheck" name="{$form.name}[]" id="{$form.name}{$key}" value="{$key}" <?php $key = (string)$key; ?> {in name="key" value="$form.value|default=''"}checked{/in} {$form.attr|default=''}> {$option|htmlspecialchars}
        </label>
        {/volist}
        {notempty name="form.tips"}
        <div class="help-block">{$form.tips}</div>
        {/notempty}
    </div>
</div>