[Unte99]

Код:

new Alives;

public OnPlayerConnect(playerid)
{
	Alives++;
	return 1;
}

public OnPlayerDisconnect(playerid, reason)
{
	Alives--;
	return 1;
}

public OnPlayerDeath(playerid, killerid, reason)
{
	Alives--;
	return 1;
}

And yes, that code will get the number of online players.