public static function updateSnapStock($num, $id) { self::initDB(); $sql = "update " . self::$table . " set snapStock=snapStock-'{$num}' where id='{$id}'"; $query = self::$dbConn->query($sql); if ($query) { return true; } else { self::$errCode = "003"; self::$errMsg = "error"; return false; } }