[SilentSoul]

pawn Код:

CMD:split(playerid, params[])
{
    new playerb, ammo, string[128];
    if(sscanf(params, "ui", playerb, ammo))
    {
        SendClientMessage(playerid, COLOR_WHITE, "USAGE: /split [playerid] [ammo]");
        return 1;
    }
    if(playerb == playerid) return SendClientMesage(playerid,-1,"You can't split ammo to yourself.");
    if(!IsPlayerLoggedIn(playerid)) return SendClientMessage(playerid, COLOR_GREY, "You need to login first before using any command.");
    if(!IsPlayerLoggedIn(playerb)) return SendClientMessage(playerid, COLOR_GREY, "Invalid player id.");
    if(!IsPlayerConnected(playerb)) return SendClientMessage(playerid,-1,"This player is not connected.");
    if(GetPlayerWeapon(playerid) == 0) return SendClientMessage(playerid,-1,"ERROR: You don't hold a weapon.");
    if(GetPlayerWeapon(playerb) == 0) return SendClientMessage(playerid,-1,"ERROR: The other player not holding a weapon.");
    if(GetPlayerAmmo(playerid) < ammo) return SendClientMessage(playerid,-1,"You don't have enough ammo.");
    SetPlayerAmmo(playerid,GetPlayerWeapon(playerid),GetPlayerAmmo(playerid)-ammo);
    SetPlayerAmmo(playerb,GetPlayerWeapon(playerb),GetPlayerAmmo(playerb)+ammo);
    format(string, sizeof(string), " You have given %s %d ammo.", RPN(playerb), ammo);
    SendClientMessage(playerid, COLOR_WHITE, string);
    format(string, sizeof(string), " %s has given you %d ammo.", RPN(playerid), ammo);
    SendClientMessage(playerb, COLOR_WHITE, string);
    return 1;
}

Not tested yet. but i think it should work, also you used extra parameter in sscanf "uii".