zencart 里的一段topselling程序赏析

<?php
if (!$this_is_home_page && $categories_displayTypes == 1) {
if(zen_has_category_subcategories($current_category_id)){
$topSelling_subcategories = array();
zen_get_subcategories($topSelling_subcategories,$current_category_id);
$topSelling_subcategories_str = implode(' or pt.categories_id = ',$topSelling_subcategories);
$suffix_sql = ' AND ( pt.categories_id ='.$topSelling_subcategories_str.')';
}else{
$suffix_sql = ' AND pt.categories_id = \''.$current_category_id.'\'';
}

$topSellingQuery = "SELECT p.`products_id`,p.`products_image`, pd.`products_name`
FROM products p, products_description pd,products_to_categories pt
WHERE pd.`language_id` = {$_SESSION['languages_id']} AND p.`products_status` = 1 AND pt.products_id=p.products_id AND pd.products_id=p.products_id ".$suffix_sql ."
ORDER BY p.`products_ordered` DESC LIMIT 5";
$topSelling = $db->Execute($topSellingQuery);
?>
<?php if ($topSelling->RecordCount()>0) {?>
<div class="allborder pad_10px">
<h2 class="red"><?php echo BASE_COMMON_TEXT_TOPSELLINGIN.zen_get_categories_name($current_category_id); ?></h2>
<ul class="top_selling">
<?php while (!$topSelling->EOF){ ?>
<li>
<a title="<?php echo $topSelling->fields['products_name']; ?>" href="<?php echo zen_href_link(zen_get_info_page($topSelling->fields['products_id']),'products_id='.$topSelling->fields['products_id']) ?>"><?php echo zen_image_OLD(DIR_WS_IMAGES.$topSelling->fields['products_image'],$topSelling->fields['products_name'],42,42,'class="fl"'); ?></a>
<span><a title="<?php echo $topSelling->fields['products_name']; ?>" href="<?php echo zen_href_link(zen_get_info_page($topSelling->fields['products_id']),'products_id='.$topSelling->fields['products_id']) ?>"><?php echo substr($topSelling->fields['products_name'],0,16).(strlen($topSelling->fields['products_name']) > 16 ? '...': ''); ?></a><br/>
<strong class="red"><?php echo $currencies->display_price((zen_get_products_base_price($topSelling->fields['products_id']) == 0 ? zen_get_products_sample_price($topSelling->fields['products_id']) : zen_get_products_base_price($topSelling->fields['products_id'])),zen_get_tax_rate($topSelling->fields['products_id'])) ?></strong>
</span>
</li>
<?php
$topSelling->MoveNext();
}
?>
</ul>
</div>
<?php }
} ?>
<?php if ($categories_displayTypes != 3){ ?>
</div>
<?php } ?>
<div class="clear"></div>
<?php } ?>