“Erreur PHP PDO 500” Réponses codées

Erreur PHP PDO 500

try {
    $dsn = "mysql:dbname=testdb;host={$db_host1}";
    $dbh = new PDO($dsn, $db_username, $db_password);
} catch (PDOException $e) {
    print "Error!: " . $e->getMessage() . "<br/>";
    die();
}