thinkphp判断商品是否存在

 <empty name="list">
                <center><div style="font-size:25px; margin-top:150px;">暂无商品</div></center>
                            <else />
                             <volist name="list" id="vo">
                            <li>
                            <div class="ncpimg"><a href="__URL__/test_list?pid={$vo.products_id}"><img width="196px" height="183px" src="../uploadfile/pic/big/{$vo.products_thumb|substr=23,14}" /></a></div>
                            <div class="ncptit"><a href="">{$vo.products_name}</a></div>
                            <div class="nprice">¥ {$vo.products_retail_price}</div>
                            </li>
                            </volist>
                            </empty>
作者：nycqwert