[Stinged]

pawn Код:

isnumeric(const string[])
{
    for (new i = 0, j = strlen(string); i < j; i++)
    {
        if (string[i] > '9' || string[i] < '0') return 0;
    }
    return 1;
}

pawn Код:

if (!isnumeric(tmp)) return SendClientMessage(playerid, -1, "USAGE: /heal [playerid]");

You really should use zcmd (or y_commands) and sscanf though, it makes creating commands much faster and easier.