如何在以前的MySQL操作中获取受影响的行？

UPDATE users SET status = 'inactive' WHERE age > 30;

SELECT ROW_COUNT();

$conn = new PDO('mysql:host=localhost;dbname=mydatabase', 'username', 'password');
$conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);

$stmt = $conn->prepare("UPDATE users SET status = 'inactive' WHERE age > 30");
$stmt->execute();

$stmt = $conn->prepare("SELECT ROW_COUNT()");
$stmt->execute();
$affected_rows = $stmt->fetchColumn();

echo "受影响的行数： $affected_rows";