foreach loop: li tag after 4 th element

<div class="home-careers">
<div class="home-careers-container">
<ul class="home-careers-slideshow">
<?php
$collection = Mage::getModel('careers/careers')->getCollection();
$counter=1; ?>
<li> <?php
foreach ($collection as $item) {
?>
<?php if($item->getfilename()!="" && $item->getstatus()==1){?>
<div class="careers-iteam-content <?php echo $counter; ?>"><?php echo $item->getContent(); ?></div><div class="careers-iteam-img"><a href="#"><img src="<?php echo Mage::getBaseUrl(Mage_Core_Model_Store::URL_TYPE_MEDIA) .$item->getfilename()?> " alt="" title=""/></a></div>
<?php } ?>
<?php if($counter%4==0): echo "</li><li>";  endif;?>
<?php $counter++; ?>
<?php } ?>
</ul>
</div>
</div>