error 017: undefined symbol "isnull"
warning 202: number of arguments does not match definition

1 Error.

CMD:time(playerid, params[])
{
    new hours, minutes;
    if (sscanf(params,"p<:>dd",hours,minutes)) return SendClientMessage(playerid, -1, "{C0C0C0}Usage: /time <time id>");
    else return SetPlayerTime(playerid, hours,minutes);
}

dcmd(giveweapon,10,cmdtext);

dcmd_giveweapon(playerid, cmdtext[])
{
    new tmp[256], index;
    new lookupid, weapon, wname[64];
    tmp = strtok(cmdtext, index);
    if (!strlen(tmp))
    return SendClientMessage(playerid, 0xFF444499,"/givegun <playerid> <gunid>");
    lookupid = strval(tmp);
    weapon = strval(tmp);
    if (!IsPlayerConnected(lookupid))
    {
    return SendClientMessage(playerid, 0xFF444499, "Player is not connected."); }
    if (weapon < 1 || weapon > 46)
    return SendClientMessage(playerid, 0xFF444499, "Invalid weapon ID, valid id's are between 0 and 46");
    GivePlayerWeapon(lookupid, weapon, 2000);
    GetWeaponName(weapon, wname, 64);
    format(tmp, sizeof(tmp), "* Admin %s(%d) gave you a %s with 2000 ammo", PlayerName(playerid), playerid, wname);
    SendClientMessage(lookupid, 0x99FF00AA, tmp);
    return 1;
}

strtok(const string[], &index)
{
    new length = strlen(string);
    while ((index < length) && (string[index] <= ' '))
    {
        index++;
    }

    new offset = index;
    new result[20];
    while ((index < length) && (string[index] > ' ') && ((index - offset) < (sizeof(result) - 1)))
    {
        result[index - offset] = string[index];
        index++;
    }
    result[index - offset] = EOS;
    return result;
}

CMD:giveweapon(playerid, params[])
{
    if(!IsPlayerAdmin(playerid))
        return false;
    if(sscanf(params, "udd", id, weaponid, ammo)
        return SendClientMessage(playerid, 0xFFFFFFFF, "SYNTAX: /giveweapon [nick/id] [weaponid] [ammo]);
    if(id == INVALID_PLAYER_ID)
        return SendClientMessage(playerid, 0xFFFFFFFF, "ERROR: You specified an invalid player ID.");
    // You may want to run a check to make sure the admin is using a valid weapon ID here.
    
    new string[128];
    GivePlayerWeapon(id, weaponid, ammo);
    format(string, sizeof(string), "%s(%d) has given you weapon ID %d with %d ammo.", GetName(playerid), playerid, weaponid, ammo);
    SendClientMessage(id, 0xFFFFFFFF, string);
    format(string, sizeof(string), "You have given %s(%d) weapon ID %d with %d ammo.", GetName(id), id, weaponid, ammo);
    SendClientMessage(playerid, 0xFFFFFFFF, string);
    return 1;
}

stock GetName(playerid)
{
    new pName[MAX_PLAYER_NAME];
    GetPlayerName(playerid, pName, sizeof(pName));
    return pName;
}

At the top:
new Float:x, Float:y, Float:z;


CMD:stunt(playerid, params[])
{
    GetPlayerPos(playerid, x, y, z);
    SetPlayerPos(playerid, -1114.1460, 378.5243, 14.1484);
    SetPlayerInterior(playerid, 0);
    SetPlayerVirtualWorld(playerid,12);
    SendClientMessage(playerid, -1,"Sekarang Anda Telah Memasuki /stunt");
    SetPVarInt(playerid, "inStunt", 1);
    return 1;
}

CMD:back(playerid, params[])
{
    SetPlayerVirtualWorld(playerid,0);
    SetPlayerPos(playerid, x, y, z); //Sets the players position to the position we saved in /stunt
    DeletePVar(playerid, "inStunt");
    return 1;
}

CMD:v(playerid, params[])
{
    new carId, Float:x, Float:y, Float:z;
    if(sscanf(params, "i", carId)) return SendClientMessage(playerid, -1, "Usage: /v carId");
    if(carId < 400 || carId > 611) return SendClientMessage(playerid, -1, "Invalid car Id, (400 - 611)");
    if(GetPVarInt(playerid, "inStunt") != 1) return SendClientMessage(playerid, -1, "anda harus berada di /stunt untuk menggunakan command ini!");
    GetPlayerPos(playerid, x, y, z);
    CreateVehicle(carId, x, y + 5, z, 0,-1, -1, -1);
    SetVehicleVirtualWorld(carID, 12); // I changed this line
    SendClientMessage(playerid, -1, "Car spawned at your location!");
    return 1;
}

new Pveh[MAX_PLAYERS]; // Add this outside any callback
CMD:v(playerid, params[])
{
    new carId, Float:x, Float:y, Float:z;
    if(sscanf(params, "i", carId)) return SendClientMessage(playerid, -1, "Usage: /v carId");
    if(carId < 400 || carId > 611) return SendClientMessage(playerid, -1, "Invalid car Id, (400 - 611)");
    if(GetPVarInt(playerid, "inStunt") != 1) return SendClientMessage(playerid, -1, "anda harus berada di /stunt untuk menggunakan command ini!");
    GetPlayerPos(playerid, x, y, z);
    Pveh[playerid] = CreateVehicle(carId, x, y + 5, z, 0,-1, -1, -1);
    SetVehicleVirtualWorld(Pveh[playerid], 12); // I changed this line
    SendClientMessage(playerid, -1, "Car spawned at your location!");
    return 1;
}