[HurtLocker]

By adding these lines, you force the cmd to accept only 1 variable, the name string:

pawn Код:

if(sscanf(params, "z", name))
        {
            SendClientMessage(playerid, WHITE, "SYNTAX: /taxi [message of the day]");
        }

You have to use only once the sscanf function like this:

pawn Код:

if(sscanf(params, "s[128]u", name, id))
{
    SendClientMessage(playerid, COLOR_WHITE, "USAGE: /taxi check [playerid]");
    return 1;
}

EDIT:

P.S.: I have also tried to make a command having a different output when I enter 1 input and another output if i enter 2 inputs, but failed.