[Luka P.]

pawn Код:

stock GetPlayersInTeam(teamid)
{
    new playersInTeam = 0;

    for(new i=0;i<MAX_PLAYERS<i++;)
    {
        if(IsPlayerConnected(i) && GetPlayerTeam(i) == teamid) playersInTeam++;
    }

    return playersInTeam;
}

With this functon you check how many players have specific team.
Example: you can create a team balancer if you're using SetPlayerTeam, not variables.

pawn Код:

public OnPlayerRequestSpawn(playerid)
{
    new pClass = GetPlayerSkin(playerid);

    switch(pClass)
    {
        case 1,2,3: SetPlayerTeam(playerid,1);
        case 4,5,6: SetPlayerTeam(playerid,2);
    }

    if(GetPlayerTeam(playerid) == 1 && GetPlayersInTeam(1) > GetPlayersInTeam(2))
    {
        SendClientMessage(playerid,color,"Team 1 is full, please choose another team/skin/class.");
        return 0;
    }

    else if(GetPlayerTeam(playerid) == 2 && GetPlayersInTeam(1) < GetPlayersInTeam(2))
    {
        SendClientMessage(playerid,color,"Team 2 is full, please choose another team/skin/class.");
        return 0;
    }

    return 1;
}

Now both codes tested, works!