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237 lines
9.1 KiB
HTML
<html>
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<title>ADODB Session Management Manual</title>
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<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
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<XSTYLE
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body,td {font-family:Arial,Helvetica,sans-serif;font-size:11pt}
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pre {font-size:9pt}
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</head>
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<body bgcolor="#FFFFFF">
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<h3>ADODB Session Management Manual</h3>
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<p>
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V4.22 15 Apr 2004 (c) 2000-2004 John Lim (jlim#natsoft.com.my)
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<p> <font size=1>This software is dual licensed using BSD-Style and LGPL. This
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means you can use it in compiled proprietary and commercial products. </font>
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<p>Useful ADOdb links: <a href=http://php.weblogs.com/adodb>Download</a> <a href=http://php.weblogs.com/adodb_manual>Other Docs</a>
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<h3>Introduction</h3>
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<p>
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We store state information specific to a user or web client in session variables. These session variables
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persist throughout a session, as the user moves from page to page.
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<p>
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To use session variables, call session_start() at the beginning of your web page,
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before your HTTP headers are sent. Then for every variable you want to keep alive
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for the duration of the session, call session_register($variable_name). By default,
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the session handler will keep track of the session by using a cookie. You can save objects
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or arrays in session variables also.
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<p>The default method of storing sessions is to store it in a file. However if
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you have special needs such as you:
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<ul>
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<li>Have multiple web servers that need to share session info</li>
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<li>Need to do special processing of each session</li>
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<li>Require notification when a session expires</li>
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</ul>
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<p>Then the ADOdb session handler provides you with the above additional capabilities
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by storing the session information as records in a database table that can be
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shared across multiple servers.
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<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
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of the session code by Ross Smith. The old session code is in adodb/session/old.
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<h4>ADOdb Session Handler Features</h4>
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<ul>
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<li>Ability to define a notification function that is called when a session expires. Typically
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used to detect session logout and release global resources.
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<li>Optimization of database writes. We crc32 the session data and only perform an update
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to the session data if there is a data change.
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<li>Support for large amounts of session data with CLOBs (see adodb-session-clob.php). Useful
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for Oracle.
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<li>Support for encrypted session data, see adodb-cryptsession.inc.php. Enabling encryption
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is simply a matter of including adodb-cryptsession.inc.php instead of adodb-session.inc.php.
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</ul>
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<h3>Setup</h3>
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<p>There are 3 session management files that you can use:
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<pre>
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adodb-session.php : The default
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adodb-session-clob.php : Use this if you are storing DATA in clobs
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adodb-cryptsession.php : Use this if you want to store encrypted session data in the database
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<strong>Examples</strong>
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<font color=#004040>
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include('adodb/adodb.inc.php');
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<b> $ADODB_SESSION_DRIVER='mysql';
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$ADODB_SESSION_CONNECT='localhost';
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$ADODB_SESSION_USER ='scott';
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$ADODB_SESSION_PWD ='tiger';
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$ADODB_SESSION_DB ='sessiondb';</b>
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<b>include('adodb/session/adodb-session.php');</b>
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session_start();
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#
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# Test session vars, the following should increment on refresh
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#
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$_SESSION['AVAR'] += 1;
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print "<p>\$_SESSION['AVAR']={$_SESSION['AVAR']}</p>";
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</font>
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To force non-persistent connections, call adodb_session_open first before session_start():
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<font color=#004040>
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include('adodb/adodb.inc.php');
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<b> $ADODB_SESSION_DRIVER='mysql';
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$ADODB_SESSION_CONNECT='localhost';
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$ADODB_SESSION_USER ='scott';
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$ADODB_SESSION_PWD ='tiger';
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$ADODB_SESSION_DB ='sessiondb';</b>
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<b>include('adodb/session/adodb-session.php');
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adodb_sess_open(false,false,false);</b>
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session_start();
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</font color=#004040>
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To use a encrypted sessions, simply replace the file:
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<font color=#004040>
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include('adodb/adodb.inc.php');
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<b> $ADODB_SESSION_DRIVER='mysql';
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$ADODB_SESSION_CONNECT='localhost';
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$ADODB_SESSION_USER ='scott';
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$ADODB_SESSION_PWD ='tiger';
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$ADODB_SESSION_DB ='sessiondb';
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include('adodb/session/adodb-cryptsession.php');</b>
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session_start();
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</font>
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And the same technique for adodb-session-clob.php:
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<font color=#004040>
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include('adodb/adodb.inc.php');
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<b> $ADODB_SESSION_DRIVER='mysql';
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$ADODB_SESSION_CONNECT='localhost';
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$ADODB_SESSION_USER ='scott';
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$ADODB_SESSION_PWD ='tiger';
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$ADODB_SESSION_DB ='sessiondb';
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include('adodb/session/adodb-session-clob.php');</b>
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session_start();
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</font>
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<h4>Installation</h4>
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1. Create this table in your database (syntax might vary depending on your db):
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<a name=sessiontab></a> <font color=#004040>
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create table sessions (
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SESSKEY char(32) not null,
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EXPIRY int(11) unsigned not null,
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EXPIREREF varchar(64),
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DATA text not null,
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primary key (sesskey)
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);</font>
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For the adodb-session-clob.php version, create this:
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<font color=#004040>
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create table sessions (
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SESSKEY char(32) not null,
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EXPIRY int(11) unsigned not null,
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EXPIREREF varchar(64),
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DATA CLOB,
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primary key (sesskey)
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);</font>
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2. Then define the following parameters. You can either modify
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this file, or define them before this file is included:
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<font color=#004040>
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$ADODB_SESSION_DRIVER='database driver, eg. mysql or ibase';
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$ADODB_SESSION_CONNECT='server to connect to';
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$ADODB_SESSION_USER ='user';
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$ADODB_SESSION_PWD ='password';
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$ADODB_SESSION_DB ='database';
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$ADODB_SESSION_TBL = 'sessions'; # setting this is optional
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</font>
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When the session is created, $<b>ADODB_SESS_CONN</b> holds the connection object.
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3. Recommended is PHP 4.0.6 or later. There are documented session bugs
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in earlier versions of PHP.
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</pre>
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<h3>Notifications</h3>
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<p>If you want to receive notification when a session expires, then
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tag the session record with a <a href="#sessiontab">EXPIREREF</a> tag (see the
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definition of the sessions table above). Before any session record is deleted,
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ADOdb will call a notification function, passing in the EXPIREREF.
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<p>
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When a session is first created, we check a global variable $ADODB_SESSION_EXPIRE_NOTIFY.
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This is an array with 2 elements, the first being the name of the session variable
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you would like to store in the EXPIREREF field, and the 2nd is the
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notification function's name.
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<p>
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Suppose we want to be notified when a user's session
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has expired, based on the userid. The user id in the global session variable $USERID.
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The function name is 'NotifyFn'. So we define:
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<pre> <font color=#004040>
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$ADODB_SESSION_EXPIRE_NOTIFY = array('USERID','NotifyFn');
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</font></pre>
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And when the NotifyFn is called (when the session expires), we pass the $USERID
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as the first parameter, eg. NotifyFn($userid, $sesskey). The session key (which is
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the primary key of the record in the sessions table) is the 2nd parameter.
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<p>
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Here is an example of a Notification function that deletes some records in the database
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and temporary files:
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<pre><font color=#004040>
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function NotifyFn($expireref, $sesskey)
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{
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global $ADODB_SESS_CONN; # the session connection object
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$user = $ADODB_SESS_CONN->qstr($expireref);
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$ADODB_SESS_CONN->Execute("delete from shopping_cart where user=$user");
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system("rm /work/tmpfiles/$expireref/*");
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}</font>
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</pre>
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<p>
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NOTE 1: If you have register_globals disabled in php.ini, then you will have to
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manually set the EXPIREREF. E.g.
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<pre> <font color=#004040>
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$GLOBALS['USERID'] =& $_SESSION['USERID'];
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$ADODB_SESSION_EXPIRE_NOTIFY = array('USERID','NotifyFn');
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</font></pre>
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<p>
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NOTE 2: If you want to change the EXPIREREF after the session record has been
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created, you will need to modify any session variable to force a database
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record update.
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<h4>Neat Notification Tricks</h4>
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<p><i>ExpireRef</i> normally holds the user id of the current session.
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<p>
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1. You can then write a session monitor, scanning expireref to see
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who is currently logged on.
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<p>
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2. If you delete the sessions record for a specific user, eg.
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<pre>
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delete from sessions where expireref = '$USER'
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</pre>
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then the user is logged out. Useful for ejecting someone from a
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site.
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<p>
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3. You can scan the sessions table to ensure no user
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can be logged in twice. Useful for security reasons.
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<p>
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<h3>Compression/Encryption Schemes</h3>
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Since ADOdb 4.05, thanks to Ross Smith, multiple encryption and compression schemes are supported.
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Currently, supported:
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<pre>
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MD5Crypt (crypt.inc.php)
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MCrypt
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Secure (Horde's emulation of MCrypt, if MCrypt module is not available.)
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GZip
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BZip2
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</pre>
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These are stackable. E.g.
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<pre>
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ADODB_Session::filter(new ADODB_Compress_Bzip2());
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ADODB_Session::filter(new ADODB_Encrypt_MD5());
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</pre>
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will compress and then encrypt the record in the database.
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<p>
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Also see the <a href=docs-adodb.htm>core ADOdb documentation</a>.
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</body>
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</html> |