我正在将PHP PDO与PostgreSQL一起用于新项目。

给定以下功能，如何返回刚刚插入的行的ID？它不像现在那样工作。

function adauga_administrator($detalii) {
    global $db;
    $ultima_logare = date('Y-m-d');

    $stmt = $db->prepare("INSERT INTO site_admins (sa_nume, sa_prenume, sa_user_name, sa_password, sa_email, sa_id_rol, sa_status, sa_ultima_logare) VALUES (?, ?, ?, ?, ?, ?, ?, ?)");
    $stmt->bindParam(1, $detalii['nume']);
    $stmt->bindParam(2, $detalii['prenume']);
    $stmt->bindParam(3, $detalii['username']);
    $stmt->bindParam(4, md5(md5($detalii['parola'] . SIGURANTA_PAROLE) . SIGURANTA_PAROLE));
    $stmt->bindParam(5, $detalii['email']);
    $stmt->bindParam(6, $detalii['rol'], PDO::PARAM_INT);
    $stmt->bindParam(7, $detalii['status'], PDO::PARAM_INT);
    $stmt->bindParam(8, $ultima_logare);    
    $stmt->execute();

    $id = $db->lastInsertId();
    return $id;
}