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<html>
<head>
<title>ADODB Session Management Manual</title>
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<h3>ADODB Session Management Manual</h3>
<p>
V4.20 22 Feb 2004 (c) 2000-2004 John Lim (jlim#natsoft.com.my)
<p> <font size=1>This software is dual licensed using BSD-Style and LGPL. This
means you can use it in compiled proprietary and commercial products. </font>
<p>Useful ADOdb links: <a href=http://php.weblogs.com/adodb>Download</a> <a href=http://php.weblogs.com/adodb_manual>Other Docs</a>
<h3>Introduction</h3>
<p>
We store state information specific to a user or web client in session variables. These session variables
persist throughout a session, as the user moves from page to page.
<p>
To use session variables, call session_start() at the beginning of your web page,
before your HTTP headers are sent. Then for every variable you want to keep alive
for the duration of the session, call session_register($variable_name). By default,
the session handler will keep track of the session by using a cookie. You can save objects
or arrays in session variables also.
<p>The default method of storing sessions is to store it in a file. However if
you have special needs such as you:
<ul>
<li>Have multiple web servers that need to share session info</li>
<li>Need to do special processing of each session</li>
<li>Require notification when a session expires</li>
</ul>
<p>Then the ADOdb session handler provides you with the above additional capabilities
by storing the session information as records in a database table that can be
shared across multiple servers.
<p><b>Important Upgrade Notice:</b> Since ADOdb 4.05, the session files have been moved to its own folder, adodb/session. This is a rewrite
of the session code by Ross Smith. The old session code is in adodb/session/old.
<h4>ADOdb Session Handler Features</h4>
<ul>
<li>Ability to define a notification function that is called when a session expires. Typically
used to detect session logout and release global resources.
<li>Optimization of database writes. We crc32 the session data and only perform an update
to the session data if there is a data change.
<li>Support for large amounts of session data with CLOBs (see adodb-session-clob.php). Useful
for Oracle.
<li>Support for encrypted session data, see adodb-cryptsession.inc.php. Enabling encryption
is simply a matter of including adodb-cryptsession.inc.php instead of adodb-session.inc.php.
</ul>
<h3>Setup</h3>
<p>There are 3 session management files that you can use:
<pre>
adodb-session.php : The default
adodb-session-clob.php : Use this if you are storing DATA in clobs
adodb-cryptsession.php : Use this if you want to store encrypted session data in the database
<strong>Examples</strong>
<font color=#004040>
include('adodb/adodb.inc.php');
<b> $ADODB_SESSION_DRIVER='mysql';
$ADODB_SESSION_CONNECT='localhost';
$ADODB_SESSION_USER ='scott';
$ADODB_SESSION_PWD ='tiger';
$ADODB_SESSION_DB ='sessiondb';</b>
<b>include('adodb/session/adodb-session.php');</b>
session_start();
#
# Test session vars, the following should increment on refresh
#
$_SESSION['AVAR'] += 1;
print "<p>\$_SESSION['AVAR']={$_SESSION['AVAR']}</p>";
</font>
To force non-persistent connections, call adodb_session_open first before session_start():
<font color=#004040>
include('adodb/adodb.inc.php');
<b> $ADODB_SESSION_DRIVER='mysql';
$ADODB_SESSION_CONNECT='localhost';
$ADODB_SESSION_USER ='scott';
$ADODB_SESSION_PWD ='tiger';
$ADODB_SESSION_DB ='sessiondb';</b>
<b>include('adodb/session/adodb-session.php');
adodb_sess_open(false,false,false);</b>
session_start();
</font color=#004040>
To use a encrypted sessions, simply replace the file:
<font color=#004040>
include('adodb/adodb.inc.php');
<b> $ADODB_SESSION_DRIVER='mysql';
$ADODB_SESSION_CONNECT='localhost';
$ADODB_SESSION_USER ='scott';
$ADODB_SESSION_PWD ='tiger';
$ADODB_SESSION_DB ='sessiondb';
include('adodb/session/adodb-cryptsession.php');</b>
session_start();
</font>
And the same technique for adodb-session-clob.php:
<font color=#004040>
include('adodb/adodb.inc.php');
<b> $ADODB_SESSION_DRIVER='mysql';
$ADODB_SESSION_CONNECT='localhost';
$ADODB_SESSION_USER ='scott';
$ADODB_SESSION_PWD ='tiger';
$ADODB_SESSION_DB ='sessiondb';
include('adodb/session/adodb-session-clob.php');</b>
session_start();
</font>
<h4>Installation</h4>
1. Create this table in your database (syntax might vary depending on your db):
<a name=sessiontab></a> <font color=#004040>
create table sessions (
SESSKEY char(32) not null,
EXPIRY int(11) unsigned not null,
EXPIREREF varchar(64),
DATA text not null,
primary key (sesskey)
);</font>
For the adodb-session-clob.php version, create this:
<font color=#004040>
create table sessions (
SESSKEY char(32) not null,
EXPIRY int(11) unsigned not null,
EXPIREREF varchar(64),
DATA CLOB,
primary key (sesskey)
);</font>
2. Then define the following parameters. You can either modify
this file, or define them before this file is included:
<font color=#004040>
$ADODB_SESSION_DRIVER='database driver, eg. mysql or ibase';
$ADODB_SESSION_CONNECT='server to connect to';
$ADODB_SESSION_USER ='user';
$ADODB_SESSION_PWD ='password';
$ADODB_SESSION_DB ='database';
$ADODB_SESSION_TBL = 'sessions'; # setting this is optional
</font>
When the session is created, $<b>ADODB_SESS_CONN</b> holds the connection object.
3. Recommended is PHP 4.0.6 or later. There are documented session bugs
in earlier versions of PHP.
</pre>
<h3>Notifications</h3>
<p>If you want to receive notification when a session expires, then
tag the session record with a <a href="#sessiontab">EXPIREREF</a> tag (see the
definition of the sessions table above). Before any session record is deleted,
ADOdb will call a notification function, passing in the EXPIREREF.
<p>
When a session is first created, we check a global variable $ADODB_SESSION_EXPIRE_NOTIFY.
This is an array with 2 elements, the first being the name of the session variable
you would like to store in the EXPIREREF field, and the 2nd is the
notification function's name.
<p>
Suppose we want to be notified when a user's session
has expired, based on the userid. The user id in the global session variable $USERID.
The function name is 'NotifyFn'. So we define:
<pre> <font color=#004040>
$ADODB_SESSION_EXPIRE_NOTIFY = array('USERID','NotifyFn');
</font></pre>
And when the NotifyFn is called (when the session expires), we pass the $USERID
as the first parameter, eg. NotifyFn($userid, $sesskey). The session key (which is
the primary key of the record in the sessions table) is the 2nd parameter.
<p>
Here is an example of a Notification function that deletes some records in the database
and temporary files:
<pre><font color=#004040>
function NotifyFn($expireref, $sesskey)
{
global $ADODB_SESS_CONN; # the session connection object
$user = $ADODB_SESS_CONN->qstr($expireref);
$ADODB_SESS_CONN->Execute("delete from shopping_cart where user=$user");
system("rm /work/tmpfiles/$expireref/*");
}</font>
</pre>
<p>
<p>
NOTE: If you want to change the EXPIREREF after the session record has been
created, you will need to modify any session variable to force a database
record update.
<h4>Compression/Encryption Schemes</h4>
Since ADOdb 4.05, thanks to Ross Smith, multiple encryption and compression schemes are supported.
Currently, supported:
<pre>
MD5Crypt (crypt.inc.php)
MCrypt
Secure (Horde's emulation of MCrypt, if MCrypt module is not available.)
GZip
BZip2
</pre>
These are stackable. E.g.
<pre>
ADODB_Session::filter(new ADODB_Compress_Bzip2());
ADODB_Session::filter(new ADODB_Encrypt_MD5());
</pre>
will compress and then encrypt the record in the database.
<p>
Also see the <a href=docs-adodb.htm>core ADOdb documentation</a>.
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