[Isolated]

pawn Код:

COMMAND:givepoop(playerid, params[])
{
    new targetid;
    if(!sscanf(params, "ui", targetid)) return SendClientMessage(playerid, -1, "USAGE: /givepoop [ID]");
    pInfo[targetid][Poop] ++;
/* You had three operators- "= ++" when you only need "++" as the statement you were using would try to set the variable to '++' */
    return 1;
}