Question

So I have two arrays that I need to update and set with in MySQL. item_id [1,2,3] and item_order[2,1,3]

Here is the items table before the array insert:

item_id item_order
  1         1 //should become 2
  2         2 // should become 1
  3         3 // should become 3

The arrays should be in pairs for the insert, 1-2, 2-1, 3-3.
How can I do this with a prepared statement efficiently and how can I test if the array items are indeed numbers?

Answer 1

Assuming you have input like this:

$item_id = array(1, 2, 3);
$item_order = array(2, 1, 3);
// and a PDO connection named $pdo

You can try something like this. (I’m also assuming you have PDO configured to throw exceptions when problems arise).

function all_numbers($input) {
  foreach($input as $o) {
    if(!is_numeric($o)) {
      return false;
    }
  }
  return true;
}

if(count($item_id) != count($item_order)) {
  throw new Exception("Input size mismatch!");
}

if(!all_numbers($item_id) || !all_numbers($item_order)) {
  throw new Exception("Invalid input format!");
}

$pairs = array_combine($item_id, $item_order);
// now $pairs will be an array(1 => 2, 2 => 1, 3 => 3);

if($pdo->beginTransaction()) {
  try {
    $stmt = $pdo->prepare('UPDATE `items` SET `item_order` = :order WHERE `item_id` = :id');

    foreach($pairs as $id => $order) {
      $stmt->execute(array(
        ':id' => $id,
        ':order' => $order,
      ));
    }
    $pdo->commit();
  } catch (Exception $E) {
    $tx->rollback();
    throw $E;
  }
} else {
  throw new Exception("PDO transaction failed: " . print_r($pdo->errorInfo(), true));
}

But it might be better to redesign your input – only pass the item_ids in the desired order and compute their item_order values automatically.