$sql = mysqli_fetch_object($db->query("SELECT username FROM member WHERE userID = 1");

$sql = $db->query("SELECT username FROM member WHERE userID = 1");
$query = $sql->fetch(PDO::FETCH_OBJ);

$query = $db->query("SELECT username FROM member WHERE userID = 1")->fetch(PDO::FETCH_OBJ);

public function run($sql, $bind = array())
{
    $stmt = $this->prepare($sql);
    $stmt->execute($bind);
    return $stmt;
}

$sql = "SELECT username FROM member WHERE userID = ?";
$name = $db->run($sql, [1])->fetchColumn();

$data = $pdo->prepare('INSERT INTO `data` (data_key, data_value) VALUES (:data_key, :data_value)')->execute($args);
$data = $pdo->prepare('UPDATE `data` SET data_value = :data_value WHERE data_key = :data_key'->execute($args);