具体的にいうとMySQLのドライバの下記のあたり http://creole.phpdb.org/trac/browser/trunk/classes/creole/drivers/mysql/MySQLConnection.php /** * Roll back (undo) the current transaction. * @throws SQLException * @return void */ protected function rollbackTrans() { if ($this->database) { if (!@mysql_select_db($this->database, $this->dblink)) { throw new SQLException('No database selected', mysql_error($this->dblink)); }