<p stlye="clear:both">
<?php
$total = count($photos); // number of images
$per_page = 6; // count of images to show per page
$current = isset($_GET['picasa_page']) ? max(1, intval($_GET['picasa_page'])) : 1; // current page number
// render pager https://codex.www.ads-software.com/Function_Reference/paginate_links
echo paginate_links( array(
'format' => add_query_arg('picasa_page', '%#%'),
'current' => $current,
'total' => round($total / $per_page)
) );
?>
</p>
<ul class="embpicasa">
<?php for($i = $current; $i < $current + $per_page; $i++): $photo = $photos[$i];?>
<li>
<a title="<?php echo $photo['title']?>" rel="lightbox[<?php echo $id?>]" target="_blank" href="<?php echo $photo['fullsize']?>">
<img src="<?php echo $photo['thumbnail']?>" alt="<?php echo $photo['title']?>" />
</a>
</li>
<?php endfor;?>
</ul>