<ul>
<?php foreach($categories as $category): ?>
<li><a href="<?=strtolower($category)?>"><?=$category?></a></li>
<?php endforeach; ?>
</ul><ul>
<?php
foreach ($categories as $category) {
$href = strtolower($category);
echo "<li><a href=\"{$href}\">{$category}</a></li>";
}
?>
</ul>