Subversion-Projekte lars-tiefland.php_share

$Id: README,v 1.3 2005/02/09 23:34:53 wez Exp $

PHP Data Objects

================

Concept: Data Access Abstraction

Goals:

1/  Be light-weight

2/  Provide common API for common database operations

3/  Be performant

4/  Keep majority of PHP specific stuff in the PDO core (such as persistent

    resource management); drivers should only have to worry about getting the

    data and not about PHP internals.

Transactions and autocommit

===========================

When you create a database handle, you *should* specify the autocommit

behaviour that you require.  PDO will default to autocommit on.

$dbh = new PDO("...", $user, $pass, array(PDO_ATTR_AUTOCOMMIT => true));

When auto-commit is on, the driver will implicitly commit each query as it is

executed.  This works fine for most simple tasks but can be significantly

slower when you are making a large number of udpates.

$dbh = new PDO("...", $user, $pass, array(PDO_ATTR_AUTOCOMMIT => false));

When auto-commit is off, you must then use $dbh->beginTransaction() to

initiate a transaction.  When your work is done, you then call $dbh->commit()

or $dbh->rollBack() to persist or abort your changes respectively.  Not all

databases support transactions.

You can change the auto-commit mode at run-time:

$dbh->setAttribute(PDO_ATTR_AUTOCOMMIT, false);

Regardless of the error handling mode set on the database handle, if the

autocommit mode cannot be changed, an exception will be thrown.

Some drivers will allow you to temporarily disable autocommit if you call

$dbh->beginTransaction().  When you commit() or rollBack() such a transaction,

the handle will switch back to autocommit mode again.  If the mode could not

be changed, an exception will be raised, as noted above.

When the database handle is closed or destroyed (or at request end for

persistent handles), the driver will implicitly rollBack().  It is your

responsibility to call commit() when you are done making changes and

autocommit is turned off.

vim:tw=78:et