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234 lines
12 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<html>
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<head>
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<title>ADODB Session Management Manual</title>
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content="text/html; charset=iso-8859-1">
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body, td {
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/*font-family: Arial, Helvetica, sans-serif;*/
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font-size: 11pt;
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</head>
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<body style="background-color: rgb(255, 255, 255);">
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<h3>ADODB Session Management Manual</h3>
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<p>
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V4.65 22 July 2005 (c) 2000-2005 John Lim (jlim#natsoft.com.my)
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</p>
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<p> <font size="1">This software is dual licensed using BSD-Style and
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LGPL. This means you can use it in compiled proprietary and commercial
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products. </font>
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<p>Useful ADOdb links: <a href="http://adodb.sourceforge.net/#download">Download</a>
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<a href="http://adodb.sourceforge.net/#docs">Other Docs</a>
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</p>
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<h3>Introduction</h3>
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<p> We store state information specific to a user or web client in
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session variables. These session variables persist throughout a
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session, as the user moves from page to page. </p>
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<p>To use session variables, call session_start() at the beginning of
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your web page, before your HTTP headers are sent. Then for every
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variable you want to keep alive for the duration of the session, call
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session_register($variable_name). By default, the session handler will
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keep track of the session by using a cookie. You can save objects or
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arrays in session variables also.
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</p>
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<p>The default method of storing sessions is to store it in a file.
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However if you have special needs such as you:
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</p>
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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>The ADOdb session handler provides you with the above
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additional capabilities by storing the session information as records
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in a database table that can be shared across multiple servers. </p>
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<p>These records will be garbage collected based on the php.ini [session] timeout settings.
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You can register a notification function to notify you when the record has expired and
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is about to be freed by the garbage collector.</p>
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<p><b>Important Upgrade Notice:</b> Since ADOdb 4.05, the session files
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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
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adodb/session/old. </p>
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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
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session expires. Typically
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used to detect session logout and release global resources. </li>
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<li>Optimization of database writes. We crc32 the session data and
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only perform an update
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to the session data if there is a data change. </li>
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<li>Support for large amounts of session data with CLOBs (see
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adodb-session-clob.php). Useful
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for Oracle. </li>
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<li>Support for encrypted session data, see
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adodb-cryptsession.inc.php. Enabling encryption is simply a matter of
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including adodb-cryptsession.inc.php instead of adodb-session.inc.php. </li>
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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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</p>
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<pre>adodb-session.php : The default<br>adodb-session-clob.php : Use this if you are storing DATA in clobs<br>adodb-cryptsession.php : Use this if you want to store encrypted session data in the database<br><br>
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</pre>
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<p><strong>Examples</strong>
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<p><pre>
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<font
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color="#004040"> include('adodb/adodb.inc.php');<br> <br><b> $ADODB_SESSION_DRIVER='mysql';<br> $ADODB_SESSION_CONNECT='localhost';<br> $ADODB_SESSION_USER ='scott';<br> $ADODB_SESSION_PWD ='tiger';<br> $ADODB_SESSION_DB ='sessiondb';</b><br> <br> <b>include('adodb/session/adodb-session.php');</b><br> session_start();<br> <br> #<br> # Test session vars, the following should increment on refresh<br> #<br> $_SESSION['AVAR'] += 1;<br> print "<p>\$_SESSION['AVAR']={$_SESSION['AVAR']}</p>";<br></font></pre>
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<p>To force non-persistent connections, call adodb_session_open() first before session_start():
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<p>
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<pre>
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<font color="#004040"><br> include('adodb/adodb.inc.php');<br> <br><b> $ADODB_SESSION_DRIVER='mysql';<br> $ADODB_SESSION_CONNECT='localhost';<br> $ADODB_SESSION_USER ='scott';<br> $ADODB_SESSION_PWD ='tiger';<br> $ADODB_SESSION_DB ='sessiondb';</b><br> <br> <b>include('adodb/session/adodb-session.php');<br> adodb_sess_open(false,false,false);</b><br> session_start();<br> </font>
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</pre>
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<p> The 3rd parameter to adodb_sess_open($path, $sessname, $connectMode) sets the connection method. You can pass in the following:</p>
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<table width="50%" border="1">
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<tr>
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<td><b>$connectMode</b></td>
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<td><b>Connection Method</b></td>
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</tr>
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<tr>
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<td>true</td>
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<td><p>PConnect( )</p></td>
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</tr>
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<tr>
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<td>false</td>
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<td>Connect( )</td>
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</tr>
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<tr>
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<td>'N'</td>
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<td>NConnect( )</td>
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</tr>
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<tr>
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<td>'P'</td>
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<td>PConnect( )</td>
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</tr>
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<tr>
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<td>'C'</td>
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<td>Connect( )</td>
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</tr>
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</table>
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<p>To use a encrypted sessions, simply replace the file adodb-session.php:</p>
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<pre> <font
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color="#004040"><br> include('adodb/adodb.inc.php');<br> <br><b> $ADODB_SESSION_DRIVER='mysql';<br> $ADODB_SESSION_CONNECT='localhost';<br> $ADODB_SESSION_USER ='scott';<br> $ADODB_SESSION_PWD ='tiger';<br> $ADODB_SESSION_DB ='sessiondb';<br> <br> include('adodb/session/adodb-cryptsession.php');</b><br> session_start();</font><br>
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</pre>
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<p>And the same technique for adodb-session-clob.php:</p>
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<pre> <font
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color="#004040"><br> include('adodb/adodb.inc.php');<br> <br><b> $ADODB_SESSION_DRIVER='mysql';<br> $ADODB_SESSION_CONNECT='localhost';<br> $ADODB_SESSION_USER ='scott';<br> $ADODB_SESSION_PWD ='tiger';<br> $ADODB_SESSION_DB ='sessiondb';<br> <br> include('adodb/session/adodb-session-clob.php');</b><br> session_start();</font>
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</pre>
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<h4>Installation</h4>
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<p>1. Create this table in your database (syntax might vary depending on your db):
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<p><pre> <a
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name="sessiontab"></a> <font color="#004040"><br> create table sessions (<br> SESSKEY char(32) not null,<br> EXPIRY int(11) unsigned not null,<br> EXPIREREF varchar(64),<br> DATA text not null,<br> primary key (sesskey)<br> );</font><br>
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</pre>
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<p> For the adodb-session-clob.php version, create this:
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<p> <pre>
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<font
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color="#004040"><br> create table sessions (<br> SESSKEY char(32) not null,<br> EXPIRY int(11) unsigned not null,<br> EXPIREREF varchar(64),<br> DATA CLOB,<br> primary key (sesskey)<br> );</font>
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</pre>
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<p>2. Then define the following parameters. You can either modify this file, or define them before this file is included:
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<pre> <font
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color="#004040"><br> $ADODB_SESSION_DRIVER='database driver, eg. mysql or ibase';<br> $ADODB_SESSION_CONNECT='server to connect to';<br> $ADODB_SESSION_USER ='user';<br> $ADODB_SESSION_PWD ='password';<br> $ADODB_SESSION_DB ='database';<br> $ADODB_SESSION_TBL = 'sessions'; # setting this is optional<br> </font>
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</pre><p>
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When the session is created, $<b>ADODB_SESS_CONN</b> holds the connection object.<br> <br> 3. Recommended is PHP 4.0.6 or later. There are documented session bugs in earlier versions of PHP.
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<h3>Notifications</h3>
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<p>You can receive notification when your session is cleaned up by the session garbage collector or
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when you call session_destroy().
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<p>PHP's session extension will automatically run a special garbage collection function based on
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your php.ini session.cookie_lifetime and session.gc_probability settings. This will in turn call
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adodb's garbage collection function, which can be setup to do notification.
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<p>
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<pre>
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PHP Session --> ADOdb Session --> Find all recs --> Send --> Delete queued
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GC Function GC Function to be deleted notification records
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executed at called by for all recs
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random time Session Extension queued for deletion
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</pre>
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<p>When a session is created, we need to store a value in the session record (in the EXPIREREF field), typically
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the userid of the session. Later when the session has expired, just before the record is deleted,
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we reload the EXPIREREF field and call the notification function with the value of EXPIREREF, which
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is the userid of the person being logged off.
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<p>ADOdb use a global variable $ADODB_SESSION_EXPIRE_NOTIFY that you must predefine before session
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start to store the notification configuratioin.
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$ADODB_SESSION_EXPIRE_NOTIFY is an array with 2 elements, the
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first being the name of the session variable you would like to store in
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the EXPIREREF field, and the 2nd is the notification function's name. </p>
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<p>For example, suppose we want to be notified when a user's session has expired,
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based on the userid. When the user logs in, we store the id in the global session variable
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$USERID. The function name is 'NotifyFn'.
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<p>
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So we define (before session_start() is called): </p>
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<pre> <font color="#004040"><br> $ADODB_SESSION_EXPIRE_NOTIFY = array('USERID','NotifyFn');<br> </font></pre>
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And when the NotifyFn is called (when the session expires), the
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$USERID is passed in as the first parameter, eg. NotifyFn($userid, $sesskey). The
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session key (which is the primary key of the record in the sessions
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table) is the 2nd parameter.
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<p> Here is an example of a Notification function that deletes some
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records in the database and temporary files: </p>
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<pre><font color="#004040"><br> function NotifyFn($expireref, $sesskey)<br> {<br> global $ADODB_SESS_CONN; # the session connection object<br><br> $user = $ADODB_SESS_CONN->qstr($expireref);<br> $ADODB_SESS_CONN->Execute("delete from shopping_cart where user=$user");<br> system("rm /work/tmpfiles/$expireref/*");<br> }</font><br> </pre>
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<p> NOTE 1: If you have register_globals disabled in php.ini, then you
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will have to manually set the EXPIREREF. E.g. </p>
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<pre> <font color="#004040">
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$GLOBALS['USERID'] =& $_SESSION['USERID'];
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$ADODB_SESSION_EXPIRE_NOTIFY = array('USERID','NotifyFn');</font>
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</pre>
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<p> NOTE 2: If you want to change the EXPIREREF after the session
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record has been created, you will need to modify any session variable
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to force a database record update.
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</p>
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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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<p>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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<p>2. If you delete the sessions record for a specific user, eg.
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</p>
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<pre>delete from sessions where expireref = '$USER'<br></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>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
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compression schemes are supported. Currently, supported are:
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<p>
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<pre> MD5Crypt (crypt.inc.php)<br> MCrypt<br> Secure (Horde's emulation of MCrypt, if MCrypt module is not available.)<br> GZip<br> BZip2<br></pre>
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<p>These are stackable. E.g.
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<p><pre>ADODB_Session::filter(new ADODB_Compress_Bzip2());<br>ADODB_Session::filter(new ADODB_Encrypt_MD5());<br></pre>
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will compress and then encrypt the record in the database.
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<h3>adodb_session_regenerate_id()</h3>
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<p>Dynamically change the current session id with a newly generated one and update database. Currently only
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works with cookies. Useful to improve security by reducing the risk of session-hijacking.
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See this article on <a href=http://shiflett.org/articles/security-corner-feb2004>Session Fixation</a> for more info
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on the theory behind this feature. Usage:
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<pre>
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$ADODB_SESSION_DRIVER='mysql';
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$ADODB_SESSION_CONNECT='localhost';
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$ADODB_SESSION_USER ='root';
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$ADODB_SESSION_PWD ='abc';
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$ADODB_SESSION_DB ='phplens';
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include('path/to/adodb/session/adodb-session.php');
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session_start();
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# Every 10 page loads, reset cookie for safety.
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# This is extremely simplistic example, better
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# to regenerate only when the user logs in or changes
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# user privilege levels.
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if ((rand()%10) == 0) adodb_session_regenerate_id(); </pre>
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<p>This function calls session_regenerate_id() internally or simulates it if the function does not exist.
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<h2>More Info</h2>
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<p>Also see the <a href="docs-adodb.htm">core ADOdb documentation</a>.
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</p>
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</body>
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</html>
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