PHP script runs but the nothing changes in the MySQL database

Question

I have a script which retrieves the details of a record and uses those details to populate a form for users to amend their details.

The following PHP script is intended to accept the details of the form (assuming some but not necessarily all fields will contain amended data) and then direct users to a success notification page.

$conn = dbConnect('admin');
//create SQL
$sql = 'UPDATE gallery_item SET price = ?, short_desc = ?, height = ?, width = ?, type = ?, long_desc = ? WHERE gallery_id = ?';
$stmt = $conn->prepare($sql);

//execute the query by passing the variables
$done = $stmt->execute(array($_POST['price'], $_POST['short_desc'], $_POST['height'], $_POST['width'], $_POST['type'], $_POST['long_desc'], $item));

//redirect if successful or display error
if ($done)
{
header('Location: http://www.mydomain.com/confirmation_success.php');
exit;
}
else
{
$error = $stmt->errorInfo();
echo $error[2];
}

The script runs without any errors and does in fact direct to a new page.
But when I check the record in the database, nothing has been updated.

I am wondering whether I need to closeCursor() before creating a new PDO object to update the record. Naturally, a database resource was previously created to retrieve the record in the first place.

But where ever I insert $result->closeCursor() it generates a fatal error.
Fatal error: Call to a member function closeCursor() on a non-object.