$productname = htmlspecialchars($_POST['pname']);
$selectprice    = htmlspecialchars($_POST['price']);

$sql="select *  from yourtable where productname LIKE '%$productname%'"; 

if($selectprice=="1") {
     $sql .= " and productprice BETWEEN 1 AND 2";
}else if($selectprice=="2") {
     $sql .= " and productprice BETWEEN 2 AND 3";  
}else if($selectprice=="3") {
     $sql .= " and productprice BETWEEN 3 AND 4";  
}