PDO's automatic submission function is enabled on MySQL with autocommit turned off

Question

I was just assigned to a legacy PHP codebase that only used PDO.

The connection is done using the following pattern:

<code>// Connect to MySQL database
$con = new mysqli($host, $user, $password, $database);
 
// Check connection
if ($con->connect_error) {
    die("Connection failed: " . $con->connect_error);
}

$con->autocommit(true);
</code>

And using that autocommit(true) works as expected even if the MySQL server is configured with SET autocommit = 0.

Now I'm trying to migrate from normal SQL to prepared statements, so I wrote this

<code>$dsn = "mysql:host=$host;dbname=$database";
$pdo = new PDO($dsn, $user, $password);
$pdo->setAttribute(PDO::ATTR_AUTOCOMMIT, true);
$pdo->setAttribute(PDO::ATTR_AUTOCOMMIT, 1);
</code>

and the example function below

<code>function updateTeam($pdo, $name, $id)
{
    try {
        $data = [
            'name' => $name,
            'id' => $id
        ];
        $sql = "UPDATE teams SET name = :name WHERE id=:id";
        $stmt = $pdo->prepare($sql);
        $stmt->execute($data);
        // $pdo->commit();
    }
    catch (PDOException $e) {
        db::$pdo->rollback();
        error_log('Failed: ' . $e->getMessage() );
    }
    catch (Exception $exc) {
        db::$pdo->rollback();
        error_log('Failed: ' . $exc->getMessage());
    }
}
</code>

Do not submit. I have to uncomment $pdo->commit(); to make it work, which I don't want because it forces me to change every query statement in the application.

What did I miss in PDO configuration? I tried var_dump($pdo->query('SELECT @@autocommit')->fetchAll()); and the result was

< /p>

array(1) { [0]=> array(2) { ["@@autocommit"]=> string(1) "0" [0]=> string(1) "0" } }

Answer 1

PDO's automatic submission is different from MySQL's automatic submission. This means that if you set the value of autocommit to default to 0 in your MySQL configuration, it will not change the default value of PDO::ATTR_AUTOCOMMIT. The default value of PDO::ATTR_AUTOCOMMIT is always true.

Changing the value of PDO::ATTR_AUTOCOMMIT to the same value or any other value that is not a boolean or integer will be ignored. This means that both operations are no-ops:

$pdo = new PDO($dsn, $user, $password);
$pdo->setAttribute(PDO::ATTR_AUTOCOMMIT, true); // 因为默认值是true
$pdo->setAttribute(PDO::ATTR_AUTOCOMMIT, 1); // 转换为布尔值true，与默认值相同

You can trick it by disabling and enabling PDO::ATTR_AUTOCOMMIT:

$pdo = new PDO($dsn, $user, $password);
$pdo->setAttribute(PDO::ATTR_AUTOCOMMIT, false);
$pdo->setAttribute(PDO::ATTR_AUTOCOMMIT, true);

This will make two calls to the MySQL server and should set MySQL's autocommit value to 1