problem binding parameter to pdo statement

Question

Having problem with binding parameters to PDO statement. "orderBy" seems not to be passed to query and results are not ordered as suppose to. When I use "price" in query itself all is good but cannot bind paremeter via bindParam. The code is:

class Products
{
 const ORDER_BY_NAME="name";
 const ORDER_BY_PRICE_PER_UNIT="price_per_unit";
 const ORDER_BY_PRICE="price";
 const ORDER_BY_MINIMUM_QUANTITY="minimum_quantity";

 // function returns array of all products

 public function getAllProducts($orderBy)
 { 
  $db=Registry::getVariable("db");

  $pdoStatement=$db->prepare("SELECT name, minimum_quantity, price_per_unit, price, id FROM products ORDER BY :orderBy;");

  $pdoStatement->bindParam(":orderBy",$orderBy,PDO::PARAM_STR);

  $pdoStatement->execute();

  return $pdoStatement->fetchAll(PDO::FETCH_ASSOC);
 }
}

and later on calling

 $products=new Products();

 echo $products->getAllProducts(Products::ORDER_BY_PRICE);

why my bindParam(":orderBy",$orderBy,PDO::PARAM_STR); dosen't seem to be used in query? any help would be much appreciated :)

Answer 1

Parameter binding is intended to be used with values. ORDER BY is actually followed by a field name, not a string.