[Mikep.]

pawn Код:

new pCheck[MAX_PLAYERS];

public OnPlayerConnect(playerid)
{
  pCheck[playerid] = 0;
  return 1;
}

public OnPlayerRequestClass(playerid, classid)
{
  if(Registered(playerid) && !pCheck[playerid]) SpawnPlayer(playerid);
  pCheck = 1;
  return 1;
}

That's how I would do it.