PHP prepared statements and transactions in a loop [duplicate]

Question

The classic transactions in a loop code:

$mysqli->query("START TRANSACTION");
foreach ($pdata as $key => $value) {
    $sql    = "INSERT INTO temp (`fund_id`) VALUES (" . $value . ")";
    $result = $mysqli->query($sql);
}
$mysqli->query("COMMIT");

Then we change to prepared statements:

$mysqli->autocommit(FALSE);
foreach ($pdata as $key => $value) {
    $sql  = "INSERT INTO temp (`fund_id`) VALUES (?)";
    $stmt = $mysqli->prepare($sql);
    $stmt->bind_param('i', $value);
    $stmt->execute();
}
$mysqli->commit();

Questions:

1) Are these two codes identical? Am I missing something in the second code with prepared statements?

2) Is $mysqli->commit() the same as $mysqli->query("COMMIT")?

3) Do I need to add $mysqli->query("START TRANSACTION"); for the prepared statements block or the transaction will automatically start when we set autocommit(FALSE)?

Answer 1

Your loop can be optimized by pulling the prepare and bind_param statements out of the loop.

$value = null;
$mysqli->autocommit(FALSE);
$sql  = "INSERT INTO temp (`fund_id`) VALUES (?)";
$stmt = $mysqli->prepare($sql);
$stmt->bind_param('i', $value);
foreach ($pdata as $value) {
    $stmt->execute();
}
$mysqli->commit();

You have turned off autocommit with your autocommit(FALSE) line and therefore don't need to use the START TRANSACTION statement.