Как вставить элемент после X и Y элемента в списке?

<?php foreach ($this->rows as $k=>$blah) : ?>

<div class="someclass">blah-blah</div>

<?php endforeach; ?>

<div class="someclass">blah-blah</div>
<div class="someclass">blah-blah</div>
<div class="someclass">FOO</div>
<div class="someclass">blah-blah</div>
<div class="someclass">blah-blah</div>
<div class="someclass">BAR</div>
<div class="someclass">blah-blah</div>
<div class="someclass">blah-blah</div>
<div class="someclass">FOO</div>
<div class="someclass">blah-blah</div>
<div class="someclass">blah-blah</div>
<div class="someclass">BAR</div>

и так далее