[cosbraa]

pawn Код:

stock GetOnlinePlayers()
{
    new amount;
    foreach(Player, i)
    {
        //if(IsPlayerConnected(i))
        amount++;
    }
    return amount;
}

This wasn't tested, though I assume it would work how you want.
I can't remember if foreach checks if the ploayer is connected manually itself. If not, just uncomment that line.

Example of use;

pawn Код:

if(GetOnlinePlayers() < 20) return SendClientMessage(playerid, -1, "There are not enough players online to do this!");