GetPlayerID(const playerName[])
{
        new GetPlayerID_NAME[MAX_PLAYER_NAME];
        for(new i = GetMaxPlayers() - 1; i != -1; i--)
    {
                if(!IsPlayerConnected(i)) continue;
                GetPlayerName(i, GetPlayerID_NAME, MAX_PLAYER_NAME);
        if(strcmp(playerName, GetPlayerID_NAME, true) == 0) return i;
    }
    return -1;
}

if(GetPlayerID("Mr.DeViLsS") == -1) return SendClientMessage(playerid, -1, "Игрок Mr.DeViLsS офлайне");
else  return SendClientMessage(playerid, -1, "Игрок Mr.DeViLsS онлайн");