class DbConnection {

    private $connection;

    public function connect()
    {
          $this->connection = new PDO('mysql:host='.DB_SERVER.';dbname='.DB_NAME, DB_USER, DB_PASS, array(PDO::MYSQL_ATTR_INIT_COMMAND => "SET NAMES utf8"));
          $this->connection->setAttribute( PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION );
    }

    public function query($query)
    {
        $result = $this->connection -> query($query);
        while ($row = $result->fetch()) {
            printf('<table><tr><td>%s</td><td>%s</td><td>%s</td></tr></table><br>',
                $row['id_ceginformacio'],
                $row['cegnev'],
                $row['vevokod']
            );
        }

        // ...
    }
}

$database = new DbConnection();
$database->connect();
$database->query("SELECT * FROM ".TBL_CEGINFORMACIO)