Magento 1 add div inside list foreach

Question

I want to add a specific div after every 3 items inside the category list. So I want to extend the code of /app/design/frontend/theme/theme/template/catalog/product/list.phtml

There is the following code that displays every product inside the category:

How can I extend this code and add a specific div after every 3 items, so I get something like this:

<div class="item-1"></div>
<div class="item-2"></div>
<div class="item-3"></div>
<div class="new-to-added-div"></div>
<div class="item-4"></div>
<div class="item-5"></div>
<div class="item-6"></div>
<div class="new-to-added-div"></div>

Answer 1

You should use the Modulo operator % :

<?php $i = 0; foreach ($_productCollection as $_product): ?>
<?php if($i > 0 && $i%3 == 0): ?>
     <div class="new-to-added-div"></div>
<?php else: ?>
     <div class="item-<?php echo $i+1 ?>"></div>
<?php endif; ?> 
<?php $i++ ?>
<?php endforeach; ?>

Answer 2

<?php $i = 0; foreach ($_productCollection as $_product): ?>
    <?php if ($i % 3 == 0): ?>
        <div class="new-to-added-div"></div>
    <?php else: ?>
        <div class="item-<?php echo $i; ?>"></div>
    <?php endif;?>
    <?php $i++; ?>
<?php endforeach; ?>