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            register_shutdown_function('MDB2_closeOpenTransactions');
        }
        $query = $this->start_transaction ? 'START TRANSACTION' : 'SET AUTOCOMMIT = 1';
        $result =& $this->_doQuery($query, true);
        if (PEAR::isError($result)) {
            return $result;
        }
        $this->in_transaction = true;
        return MDB2_OK;
    }

    // }}}
    // {{{ commit()

    /**
     * Commit the database changes done during a transaction that is in
     * progress or release a savepoint. This function may only be called when
     * auto-committing is disabled, otherwise it will fail. Therefore, a new
     * transaction is implicitly started after committing the pending changes.
     *
     * @param   string  name of a savepoint to release
     * @return  mixed   MDB2_OK on success, a MDB2 error on failure
     *
     * @access  public
     */
    function commit($savepoint = null)
    {
        $this->debug('Committing transaction/savepoint', __FUNCTION__, array('is_manip' => true, 'savepoint' => $savepoint));
        if (!$this->in_transaction) {
            return $this->raiseError(MDB2_ERROR_INVALID, null, null,
                'commit/release savepoint cannot be done changes are auto committed', __FUNCTION__);
        }
        if (!is_null($savepoint)) {
            if (!$this->supports('savepoints')) {
                return $this->raiseError(MDB2_ERROR_UNSUPPORTED, null, null,
                    'savepoints are not supported', __FUNCTION__);
            }
            $server_info = $this->getServerVersion();
            if (version_compare($server_info['major'].'.'.$server_info['minor'].'.'.$server_info['patch'], '5.0.3', '<')) {
                return MDB2_OK;
            }
            $query = 'RELEASE SAVEPOINT '.$savepoint;
            return $this->_doQuery($query, true);
        }

        if (!$this->supports('transactions')) {
            return $this->raiseError(MDB2_ERROR_UNSUPPORTED, null, null,
                'transactions are not supported', __FUNCTION__);
        }

        $result =& $this->_doQuery('COMMIT', true);
        if (PEAR::isError($result)) {
            return $result;
        }
        if (!$this->start_transaction) {
            $query = 'SET AUTOCOMMIT = 0';
            $result =& $this->_doQuery($query, true);
            if (PEAR::isError($result)) {
                return $result;
            }
        }
        $this->in_transaction = false;
        return MDB2_OK;
    }

    // }}}
    // {{{ rollback()

    /**
     * Cancel any database changes done during a transaction or since a specific
     * savepoint that is in progress. This function may only be called when
     * auto-committing is disabled, otherwise it will fail. Therefore, a new
     * transaction is implicitly started after canceling the pending changes.
     *
     * @param   string  name of a savepoint to rollback to
     * @return  mixed   MDB2_OK on success, a MDB2 error on failure
     *
     * @access  public
     */
    function rollback($savepoint = null)
    {
        $this->debug('Rolling back transaction/savepoint', __FUNCTION__, array('is_manip' => true, 'savepoint' => $savepoint));
        if (!$this->in_transaction) {
            return $this->raiseError(MDB2_ERROR_INVALID, null, null,
                'rollback cannot be done changes are auto committed', __FUNCTION__);
        }
        if (!is_null($savepoint)) {
            if (!$this->supports('savepoints')) {
                return $this->raiseError(MDB2_ERROR_UNSUPPORTED, null, null,
                    'savepoints are not supported', __FUNCTION__);
            }
            $query = 'ROLLBACK TO SAVEPOINT '.$savepoint;
            return $this->_doQuery($query, true);
        }

        $query = 'ROLLBACK';
        $result =& $this->_doQuery($query, true);
        if (PEAR::isError($result)) {
            return $result;
        }
        if (!$this->start_transaction) {
            $query = 'SET AUTOCOMMIT = 0';
            $result =& $this->_doQuery($query, true);
            if (PEAR::isError($result)) {
                return $result;
            }
        }
        $this->in_transaction = false;
        return MDB2_OK;
    }

    // }}}
    // {{{ function setTransactionIsolation()

    /**
     * Set the transacton isolation level.
     *
     * @param   string  standard isolation level
     *                  READ UNCOMMITTED (allows dirty reads)
     *                  READ COMMITTED (prevents dirty reads)
     *                  REPEATABLE READ (prevents nonrepeatable reads)
     *                  SERIALIZABLE (prevents phantom reads)
     * @return  mixed   MDB2_OK on success, a MDB2 error on failure
     *
     * @access  public
     * @since   2.1.1
     */
    function setTransactionIsolation($isolation)
    {
        $this->debug('Setting transaction isolation level', __FUNCTION__, array('is_manip' => true));
        if (!$this->supports('transactions')) {
            return $this->raiseError(MDB2_ERROR_UNSUPPORTED, null, null,
                'transactions are not supported', __FUNCTION__);
        }
        switch ($isolation) {
        case 'READ UNCOMMITTED':
        case 'READ COMMITTED':
        case 'REPEATABLE READ':
        case 'SERIALIZABLE':
            break;
        default:
            return $this->raiseError(MDB2_ERROR_UNSUPPORTED, null, null,
                'isolation level is not supported: '.$isolation, __FUNCTION__);
        }

        $query = "SET SESSION TRANSACTION ISOLATION LEVEL $isolation";
        return $this->_doQuery($query, true);
    }

    // }}}
    // {{{ _doConnect()

    /**
     * do the grunt work of the connect
     *
     * @return connection on success or MDB2 Error Object on failure
     * @access protected
     */
    function _doConnect($username, $password, $persistent = false)
    {
        if (!PEAR::loadExtension($this->phptype)) {
            return $this->raiseError(MDB2_ERROR_NOT_FOUND, null, null,
                'extension '.$this->phptype.' is not compiled into PHP', __FUNCTION__);
        }

        $params = array();
        if ($this->dsn['protocol'] && $this->dsn['protocol'] == 'unix') {
            $params[0] = ':' . $this->dsn['socket'];
        } else {
            $params[0] = $this->dsn['hostspec'] ? $this->dsn['hostspec']
                         : 'localhost';
            if ($this->dsn['port']) {
                $params[0].= ':' . $this->dsn['port'];
            }
        }
        $params[] = $username ? $username : null;
        $params[] = $password ? $password : null;
        if (!$persistent) {
            if (isset($this->dsn['new_link'])
                && ($this->dsn['new_link'] == 'true' || $this->dsn['new_link'] === true)
            ) {
                $params[] = true;
            } else {
                $params[] = false;
            }
        }
        if (version_compare(phpversion(), '4.3.0', '>=')) {
            $params[] = isset($this->dsn['client_flags'])
                ? $this->dsn['client_flags'] : null;
        }
        $connect_function = $persistent ? 'mysql_pconnect' : 'mysql_connect';

        $connection = @call_user_func_array($connect_function, $params);
        if (!$connection) {
            if (($err = @mysql_error()) != '') {
                return $this->raiseError(MDB2_ERROR_CONNECT_FAILED, null, null,
                    $err, __FUNCTION__);
            } else {
                return $this->raiseError(MDB2_ERROR_CONNECT_FAILED, null, null,
                    'unable to establish a connection', __FUNCTION__);
            }
        }

        if (!empty($this->dsn['charset'])) {
            $result = $this->setCharset($this->dsn['charset'], $connection);
            if (PEAR::isError($result)) {
                $this->disconnect(false);
                return $result;
            }
        }

        return $connection;
    }

    // }}}
    // {{{ connect()

    /**
     * Connect to the database
     *
     * @return MDB2_OK on success, MDB2 Error Object on failure
     * @access public
     */
    function connect()
    {
        if (is_resource($this->connection)) {
            //if (count(array_diff($this->connected_dsn, $this->dsn)) == 0
            if (MDB2::areEquals($this->connected_dsn, $this->dsn)
                && $this->opened_persistent == $this->options['persistent']
            ) {
                return MDB2_OK;
            }
            $this->disconnect(false);
        }

        $connection = $this->_doConnect(
            $this->dsn['username'],
            $this->dsn['password'],
            $this->options['persistent']
        );
        if (PEAR::isError($connection)) {
            return $connection;
        }

        $this->connection = $connection;
        $this->connected_dsn = $this->dsn;
        $this->connected_database_name = '';
        $this->opened_persistent = $this->options['persistent'];
        $this->dbsyntax = $this->dsn['dbsyntax'] ? $this->dsn['dbsyntax'] : $this->phptype;

        if ($this->database_name) {
            if ($this->database_name != $this->connected_database_name) {
                if (!@mysql_select_db($this->database_name, $connection)) {
                    $err = $this->raiseError(null, null, null,
                        'Could not select the database: '.$this->database_name, __FUNCTION__);
                    return $err;
                }
                $this->connected_database_name = $this->database_name;
            }
        }

        $this->_getServerCapabilities();

        return MDB2_OK;
    }

    // }}}
    // {{{ setCharset()

    /**
     * Set the charset on the current connection
     *
     * @param string    charset (or array(charset, collation))
     * @param resource  connection handle
     *
     * @return true on success, MDB2 Error Object on failure
     */
    function setCharset($charset, $connection = null)
    {
        if (is_null($connection)) {
            $connection = $this->getConnection();
            if (PEAR::isError($connection)) {
                return $connection;
            }
        }
        $collation = null;
        if (is_array($charset) && 2 == count($charset)) {
            $collation = array_pop($charset);
            $charset   = array_pop($charset);
        }
        $query = "SET NAMES '".mysql_real_escape_string($charset, $connection)."'";
        if (!is_null($collation)) {
            $query .= " COLLATE '".mysqli_real_escape_string($connection, $collation)."'";
        }
        return $this->_doQuery($query, true, $connection);
    }

    // }}}
    // {{{ databaseExists()

    /**
     * check if given database name is exists?
     *
     * @param string $name    name of the database that should be checked
     *
     * @return mixed true/false on success, a MDB2 error on failure
     * @access public
     */
    function databaseExists($name)
    {
        $connection = $this->_doConnect($this->dsn['username'],
                                        $this->dsn['password'],
                                        $this->options['persistent']);
        if (PEAR::isError($connection)) {
            return $connection;
        }

        $result = @mysql_select_db($name, $connection);
        @mysql_close($connection);

        return $result;
    }

    // }}}
    // {{{ disconnect()

    /**
     * Log out and disconnect from the database.
     *
     * @param  boolean $force if the disconnect should be forced even if the
     *                        connection is opened persistently
     * @return mixed true on success, false if not connected and error
     *                object on error
     * @access public
     */
    function disconnect($force = true)
    {