ecshop搜索页如何增加属性筛选

sql的 where根据筛选条件改变而改变,举个例子：

$filter['brand'] = isset($_REQUEST['brand']) ? trim($_REQUEST['brand']) : '';//品牌
$filter['price'] = isset($_REQUEST['price']) ? trim($_REQUEST['price']) : '';//价格
$filter['attribute'] = isset($_REQUEST['attribute']) ? trim($_REQUEST['attribute']) : '';//属性

$where = " WHERE 1";
if($filter['brand'] != ''){
    $where .= " AND brand=" . addslashes($filter['brand']);
}
if($filter['price'] != ''){
    $where .= " AND price=" . addslashes($filter['price']);
}
if($filter['attribute'] != ''){
    $where .= " AND attribute=" . addslashes($filter['attribute']);
}