名称： product_data($key='')
功能： 按商品id或自定义名称读取商品数据，默认无需传参系统自动从URL读取商品id
代码示例：
<h1>{$product_data['name']}</h1>
<div class="price-availability-block clearfix">
<div class="price">
<strong><span>￥</span>{$product_data['price']}</strong>
<em>￥<span>{$product_data['price']}</span></em>
</div>
<div class="availability">
库存状态: <strong>正常</strong>
</div>
</div>
<div class="description">
<p>{$product_data['description']}</p>
</div> 数据格式打印：
Array
(
[id] => 46
[cat_id] => 15
[filename] =>
[name] => 女装2018春季新款蝙蝠袖褶皱廓形衬衫8300053
[price] => 400
[weight] => 0.18
[sn] =>
[title] => 女装2018春季新款蝙蝠袖褶皱廓形衬衫8300053
[keywords] => 咖色 蓝色 S M
[description] => 女装2018春季新款蝙蝠袖褶皱廓形衬衫8300053
[content] => ...
[image] => Array
(
[0] => /esite_static/upload/image/day_180523/eac58b9a046afb29e2df2db84b7a6cf2.jpg
[1] => /esite_static/upload/image/day_180523/3a98f77ac6721a801cedb4c30089679b.jpg
)
[edit_time] => 1527078318
[sort] => 0
[ext1] =>
[ext2] =>
[ext3] =>
[ext4] =>
[ext5] =>
[ext6] =>
[ext7] =>
[ext8] =>
[ext9] =>
[ext10] =>
[ext11] =>
[ext12] =>
[ext13] =>
[ext14] =>
[ext15] =>
[cat_unique_id] => 女士衬衫
[product_url] => /女士衬衫/46-product.html
[category_url] => /女士衬衫/p1-products.html
)