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：

$filter[&＃39;brand&＃39;] = isset($_REQUEST[&＃39;brand&＃39;]) ? trim($_REQUEST[&＃39;brand&＃39;]) : &＃39;&＃39;;//品牌
$filter[&＃39;price&＃39;] = isset($_REQUEST[&＃39;price&＃39;]) ? trim($_REQUEST[&＃39;price&＃39;]) : &＃39;&＃39;;//价格
$filter[&＃39;attribute&＃39;] = isset($_REQUEST[&＃39;attribute&＃39;]) ? trim($_REQUEST[&＃39;attribute&＃39;]) : &＃39;&＃39;;//属性

$where = " WHERE 1";
if($filter[&＃39;brand&＃39;] != &＃39;&＃39;){
    $where .= " AND brand=" . addslashes($filter[&＃39;brand&＃39;]);
}
if($filter[&＃39;price&＃39;] != &＃39;&＃39;){
    $where .= " AND price=" . addslashes($filter[&＃39;price&＃39;]);
}
if($filter[&＃39;attribute&＃39;] != &＃39;&＃39;){
    $where .= " AND attribute=" . addslashes($filter[&＃39;attribute&＃39;]);
}