Vraagje van een PDO newbie

Ik probeer mijn oude scripts om te zetten naar PDO.
Hiervoor wel wat oefenen en direct gaat het fout.
Kan iemend mij vertellen wat ik in onderstaande code fout doe:

function getAllData($db) {
   $stmt = $db->query("	
    SELECT person.*, horse.*, 2010Combination.* 
	FROM FEIPerson AS person
	INNER JOIN 2010Combination ON person.fei_id = 2010Combination.personFEIid 
	INNER JOIN FEIHorse horse ON horse.fei_id = 2010Combination.horseFEIid 
	ORDER BY person.competing_for_country, horse.complete_name ASC
    ");
    
   return $stmt->fetchAll(PDO::FETCH_ASSOC);
}

$db = new PDO('mysql:host=localhost;dbname='.$MySqlDatabase.';charset=utf8', $MySqlUsername, $MySqlPassword);

try {
   getAllData($db);
    } catch(PDOException $ex) {
        echo "An Error occurred!"; //user friendly message
    }
    
$row_count = $stmt->rowCount();
echo $row_count.' rows selected';
?>

Ik krijg deze foutmeldingen:
Notice: Undefined variable: stmt in /home/harry-arends.nl/public_html/event/SetCompNum.php on line 25

Fatal error: Call to a member function rowCount() on a non-object in /home/harry-arends.nl/public_html/event/SetCompNum.php on line 25