Why Can't I Use PDO Parameters in the ORDER BY Clause of My SQL Statement?

ORDER BY Params in PDO Statements

You encounter difficulty using parameters in the ORDER BY clause of your SQL statement. The :order and :direction params fail to produce any results.

Cause of the Issue

PDO parameters cannot be used directly in the ORDER BY clause. They must be static strings.

Solution

There are no PDO constants for column names or sorting directions. Therefore, you must insert these values directly into the SQL statement. However, it's crucial to take precautions:

1. Hardcode every operator and identifier in your script.

$orders = array("name", "price", "qty");
$key = array_search($_GET['sort'], $orders);
$order = $orders[$key];
$query = "SELECT * from table WHERE is_live = :is_live ORDER BY $order";

2. Use a whitelisting helper function:

$order = white_list($order, ["name", "price", "qty"], "Invalid field name");
$direction = white_list($direction, ["ASC", "DESC"], "Invalid ORDER BY direction");

$sql = "SELECT field from table WHERE column = ? ORDER BY $order $direction";
$stmt = $db->prepare($sql);
$stmt->execute([$is_live]);

Explanation

The whitelisting function checks the value and raises an error if it is incorrect, mitigating the risk of SQL injection attacks.

Example

$sql = "SELECT field from table WHERE column = :my_param";

$stmt = $db->prepare($sql);
$stmt->bindParam(':my_param', $is_live, PDO::PARAM_STR);
$stmt->bindParam(':order', $order, PDO::PARAM_STR);
$stmt->bindParam(':direction', $direction, PDO::PARAM_STR);
$stmt->execute();

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