public function connect($host, $db, $user, $password)
 {
     if ($this->driver == 'mysql') {
         $MM = new MySQLManager();
         $MM->setHost($host);
         $MM->setDB($db);
         $MM->setUserName($user);
         $MM->setPassword($password);
         $MM->connect();
     } elseif ($this->driver == 'pgsql') {
         $MM = new PostgreSQLManager();
         $MM->setHost($host);
         $MM->setDB($db);
         $MM->setUserName($user);
         $MM->setPassword($password);
         $MM->connect();
     }
 }