[Konstantinos]

pawn Код:

new
    bool: isfull
;

for(new i = 0; i < 10; i++)
{
    if(!PlayerInfo[playerid][pSlot][i])
    {
        PlayerInfo[playerid][pSlot][i] = item;
        isfull = true;
        break;
    }
}

if(!isfull) SendClientMessage(playerid, COLOR_RED, "ERROR:{FFFFFF} Your inventory is full.");
// You may return the message, that depends on what you want.