[Konstantinos]

There are tons of tutorials about how to use ZCMD and also converting strcmp + strtok to ZCMD + sscanf.

You will need to change as the user above said.

pawn Код:

public OnPlayerCommandText(playerid, cmdtext[])
{
    if(!strcmp(cmdtext, "/help", true))
    {
        SendClientMessage(playerid, 0xFFFFFFFF, "SERVER: This is the /help command!");
        return 1;
    }
    return 0;
}

To

pawn Код:

CMD:help(playerid, params[])
{
    SendClientMessage(playerid, 0xFFFFFFFF, "SERVER: This is the /help command!");
    return 1;
}

And NEVER inside any callback.