[Konstantinos]

"id" is the player ID and not the vehicle ID.
The "seatid" shouldn't be 0 but the first passenger (1).

PHP код:

CMD:gv(playerid, params[])
{
    if(!PlayerAcc[playerid][Log]) return SendClientMessage(playerid, COLOR_RED, "Error: You are not logged in!");
    if(PlayerAcc[playerid][Admin] >= 3)
    {
        new id;
        if(sscanf(params, "u", id)) return SendClientMessage(playerid, COLOR_RED, "Gv: /gv (id)");
        if(id == INVALID_PLAYER_ID) return ErrorMessages(playerid, 2);
        if(id == playerid) return ErrorMessages(playerid, 4);
        if(GetPlayerState(id) != PLAYER_STATE_DRIVER) return SendClientMessage(playerid, COLOR_GREY, "The player is not a driver");
        if(GetPlayerState(playerid) != PLAYER_STATE_ONFOOT) return SendClientMessage(playerid, COLOR_GREY, "You must be on foot");
        PutPlayerInVehicle(playerid, GetPlayerVehicleID(id), 1);
    }
    return 1;
}