Подключение PDO в ООП

class Db {
    public static function getConnection() {
        $paramsPath = ROOT . '/config/db_params.php';
        $params = include($paramsPath);
        $dsn = "mysql:host={$params['host']};dbname={$params['dbname']}";
        $db = new PDO($dsn, $params['user'], $params['password']);
        $db->exec("set names utf8");
        return $db;
    }
}

public static function deleteAdvt($id) {
        $id = intval($id);
        $db = Db::getConnection();
        $sql = ("DELETE FROM advt WHERE id = :id");
        $result = $db->prepare($sql);
        $result->bindParam(':id', $id, PDO::PARAM_INT);
        return $result->execute();
    }

class Db {
    private static $connections = [];
 
    public static function getConnection($connectionName) {
        if (empty(self::connections[$connectionName])) {
            $paramsPath = ROOT . '/config/db_params.php';
            $params = include($paramsPath);
            $dsn = "mysql:host={$params['host']};dbname={$params['dbname']}";
            $db = new PDO($dsn, $params['user'], $params['password']);
            $db->exec("set names utf8");
            self::connections[$connectionName] = $db;
        }
        return self::connections[$connectionName];
    }
}

public static function getAdvtById($id) {
        $id = intval($id);
        $db = Db::getConnection();
        $result = $db->query("SELECT * FROM advt "
                . "WHERE id=$id ");
        $result->setFetchMode(PDO::FETCH_ASSOC);
        return $result->fetch();
    }

public static function deleteAdvt($id) {
        $id = intval($id);
        $db = Db::getConnection();
        $sql = ("DELETE FROM advt WHERE id = :id");
        $result = $db->prepare($sql);
        $result->bindParam(':id', $id, PDO::PARAM_INT);
        return $result->execute();
    }

$db1 = Db::getConnection();
$db2 = Db::getConnection();
$db3 = Db::getConnection();
$db4 = Db::getConnection();
$db5 = Db::getConnection();

  $sql = ("DELETE FROM advt WHERE id = :id");
        $result = $db->prepare($sql);
        $result->bindParam(':id', $id, PDO::PARAM_INT);
        return $result->execute();