How do I use pdo's prepared statement for order by and limit clauses?

Question

I want to use a prepared statement in which the passed-in parameters are for the ORDER BY and LIMIT clauses, like so:

$sql = 'SELECT * FROM table ORDER BY :sort :dir LIMIT :start, :results';
$stmt = $dbh->prepare($sql);
$stmt->execute(array(
     'sort'  => $_GET['sort'], 
     'dir'  => $_GET['dir'], 
     'start'  => $_GET['start'],
     'results' => $_GET['results'],
     )
    );

But $stmt->fetchAll(PDO::FETCH_ASSOC); returns nothing.

Can someone point out what's the wrong thing I am doing? Can it be done? If not,what should I reference for a complete list of clauses where parameters can be used?

Answer 1

After using :

$dbh->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);

I got the message :

Uncaught exception 'PDOException' with message 'SQLSTATE[42000]: Syntax error or access violation: 1064 You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near ''0', '10'' at line 1

So, when you use an array for execute, it consider your inputs as string which is not a good idea for LIMIT

$dbh->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
$sql = "SELECT * FROM table ORDER BY :sort :dir LIMIT :start, :results";
$stmt = $dbh->prepare($sql);
$stmt->bindParam(':start', $_GET['start'], PDO::PARAM_INT);
$stmt->bindParam(':results', $_GET['results'], PDO::PARAM_INT);
$stmt->bindParam(':sort', $_GET['sort']);
$stmt->bindParam(':dir', $_GET['dir']);
$stmt->execute();

$data = $stmt->fetchAll(PDO::FETCH_ASSOC);
print_r($data);