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4  <title>ADODB Old Session Management Manual</title>
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22<h3>ADODB Session Management Manual</h3>
23<p>
24V4.94 23 Jan 2007 (c) 2000-2007 John Lim (jlim#natsoft.com.my)
25</p>
26<p> <font size="1">This software is dual licensed using BSD-Style and
27LGPL. This means you can use it in compiled proprietary and commercial
28products. </font>
29<p>Useful ADOdb links: <a href="http://adodb.sourceforge.net/#download">Download</a>
30&nbsp; <a href="http://adodb.sourceforge.net/#docs">Other Docs</a>
31</p>
32<h3>Introduction</h3>
33<p>This documentation discusses the old adodb-session.php.
34Here is the <a href=docs-session.htm>new documentation</a> on the newer adodb-session2.php.
35<p> We store state information specific to a user or web client in
36session variables. These session variables persist throughout a
37session, as the user moves from page to page. </p>
38<p>To use session variables, call session_start() at the beginning of
39your web page, before your HTTP headers are sent. Then for every
40variable you want to keep alive for the duration of the session, call
41session_register($variable_name). By default, the session handler will
42keep track of the session by using a cookie. You can save objects or
43arrays in session variables also.
44</p>
45<p>The default method of storing sessions is to store it in a file.
46However if you have special needs such as you:
47</p>
48<ul>
49  <li>Have multiple web servers that need to share session info</li>
50  <li>Need to do special processing of each session</li>
51  <li>Require notification when a session expires</li>
52</ul>
53<p>The ADOdb session handler provides you with the above
54additional capabilities by storing the session information as records
55in a database table that can be shared across multiple servers. </p>
56<p>These records will be garbage collected based on the php.ini [session] timeout settings.
57You can register a notification function to notify you when the record has expired and
58is about to be freed by the garbage collector.</p>
59<p><b>Important Upgrade Notice:</b> Since ADOdb 4.05, the session files
60have been moved to its own folder, adodb/session. This is a rewrite
61of the session code by Ross Smith. The old session code is in
62adodb/session/old. </p>
63<h4>ADOdb Session Handler Features</h4>
64<ul>
65  <li>Ability to define a notification function that is called when a
66session expires. Typically
67used to detect session logout and release global resources. </li>
68  <li>Optimization of database writes. We crc32 the session data and
69only perform an update
70to the session data if there is a data change. </li>
71  <li>Support for large amounts of session data with CLOBs (see
72adodb-session-clob.php). Useful
73for Oracle. </li>
74  <li>Support for encrypted session data, see
75adodb-cryptsession.php. Enabling encryption is simply a matter of
76including adodb-cryptsession.php instead of adodb-session.php. </li>
77</ul>
78<h3>Setup</h3>
79<p>There are 3 session management files that you can use:
80</p>
81<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>
82</pre>
83<p><strong>Examples</strong>
84<p><pre>
85 <font
86 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>    $_SESSION['AVAR'] += 1;<br>    print "&lt;p&gt;\$_SESSION['AVAR']={$_SESSION['AVAR']}&lt;/p&gt;";<br></font></pre>
87 
88<p>To force non-persistent connections, call adodb_session_open() first before session_start():
89<p>
90 <pre>
91 <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>    $ADODB_SESSION_DB ='sessiondb';</b><br>    <br>    <b>include('adodb/session/adodb-session.php');<br>    adodb_sess_open(false,false,false);</b><br>    session_start();<br> </font>
92 </pre>
93<p> The 3rd parameter to adodb_sess_open($path, $sessname, $connectMode)  sets the connection method. You can pass in the following:</p>
94<table width="50%" border="1">
95  <tr>
96    <td><b>$connectMode</b></td>
97    <td><b>Connection Method</b></td>
98  </tr>
99  <tr>
100    <td>true</td>
101    <td><p>PConnect( )</p></td>
102  </tr>
103  <tr>
104    <td>false</td>
105    <td>Connect( )</td>
106  </tr>
107  <tr>
108    <td>'N'</td>
109    <td>NConnect( )</td>
110  </tr>
111  <tr>
112    <td>'P'</td>
113    <td>PConnect( )</td>
114  </tr>
115  <tr>
116    <td>'C'</td>
117    <td>Connect( )</td>
118  </tr>
119</table>
120<p>To use a encrypted sessions, simply replace the file adodb-session.php:</p>
121 <pre> <font
122 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>
123 </pre>
124 <p>And the same technique for adodb-session-clob.php:</p>
125 <pre>  <font
126 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>
127 </pre>
128 <p>An alternative way to set persistant or non-persistent connections is to call the following function before session_start() is called.
129 <pre>
130        ADODB_Session::persist('P'); # 'C' for non-persistent connections
131 </pre>
132 <h4>Installation</h4>
133<p>1. Create this table in your database (MySQL syntax):
134<p><pre> <a
135 name="sessiontab"></a> <font color="#004040">
136   create table sessions (
137       SESSKEY char(32) not null,
138       EXPIRY int(11) unsigned not null,
139       EXPIREREF varchar(64),
140           DATA text not null,
141           primary key (sesskey)
142           );</font>
143 </pre>
144
145 <p>You may want to rename the 'data' field to 'session_data' as
146        'data' appears to be a reserved word for one or more of the following:
147        <ul>
148        <li>    ANSI SQL
149        <li>    IBM DB2
150        <li>    MS SQL Server
151        <li>    Postgres
152        <li>    SAP
153                </ul>
154<p>
155        If you do, then execute:
156<pre>
157                ADODB_Session::dataFieldName('session_data');
158</pre>
159 <p> For the adodb-session-clob.php version, create this:
160<p>  <pre>
161    <font
162 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>
163 </pre>
164 <p>2. Then define the following parameters. You can either modify this file, or define them before this file is included:
165 <pre>      <font
166 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>
167 </pre><p>
168     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.
169<h3>Notifications</h3>
170<p>You can receive notification when your session is cleaned up by the session garbage collector or
171when you call session_destroy().
172<p>PHP's session extension will automatically run a special garbage collection function based on
173your php.ini session.cookie_lifetime and session.gc_probability settings. This will in turn call
174adodb's garbage collection function, which can be setup to do notification.
175<p>
176<pre>
177        PHP Session --> ADOdb Session  --> Find all recs  --> Send          --> Delete queued
178        GC Function     GC Function        to be deleted      notification      records
179        executed at     called by                             for all recs
180        random time     Session Extension                     queued for deletion
181</pre>
182<p>When a session is created, we need to store a value in the session record (in the EXPIREREF field), typically
183the userid of the session. Later when the session has expired,  just before the record is deleted,
184we reload the EXPIREREF field and call the notification function with the value of EXPIREREF, which
185is the userid of the person being logged off.
186<p>ADOdb uses a global variable $ADODB_SESSION_EXPIRE_NOTIFY that you must predefine before session
187start to store the notification configuration.
188$ADODB_SESSION_EXPIRE_NOTIFY is an array with 2 elements, the
189first being the name of the session variable you would like to store in
190the EXPIREREF field, and the 2nd is the notification function's name. </p>
191<p>For example, suppose we want to be notified when a user's session has expired,
192based on the userid. When the user logs in, we store the id in the global session variable
193$USERID. The function name is 'NotifyFn'.
194<p>
195So we define (before session_start() is called): </p>
196<pre> <font color="#004040">
197        $ADODB_SESSION_EXPIRE_NOTIFY = array('USERID','NotifyFn');
198</font></pre>
199And when the NotifyFn is called (when the session expires), the
200$USERID is passed in as the first parameter, eg. NotifyFn($userid, $sesskey). The
201session key (which is the primary key of the record in the sessions
202table) is the 2nd parameter.
203<p> Here is an example of a Notification function that deletes some
204records in the database and temporary files: </p>
205<pre><font color="#004040">
206        function NotifyFn($expireref, $sesskey)
207        {
208                global $ADODB_SESS_CONN; # the session connection object
209                $user = $ADODB_SESS_CONN-&gt;qstr($expireref);
210               
211                $ADODB_SESS_CONN-&gt;Execute("delete from shopping_cart where user=$user");         
212                system("rm /work/tmpfiles/$expireref/*");
213        }</font> 
214                          </pre>
215<p> NOTE 1: If you have register_globals disabled in php.ini, then you
216will have to manually set the EXPIREREF. E.g. </p>
217<pre> <font color="#004040">
218$GLOBALS['USERID'] = GetUserID();
219$ADODB_SESSION_EXPIRE_NOTIFY = array('USERID','NotifyFn');</font>
220</pre>
221<p> NOTE 2: If you want to change the EXPIREREF after the session
222record has been created, you will need to modify any session variable
223to force a database record update.
224</p>
225<h4>Neat Notification Tricks</h4>
226<p><i>ExpireRef</i> normally holds the user id of the current session.
227</p>
228<p>1. You can then write a session monitor, scanning expireref to see
229who is currently logged on.
230</p>
231<p>2. If you delete the sessions record for a specific user, eg.
232</p>
233<pre>delete from sessions where expireref = '$USER'<br></pre>
234then the user is logged out. Useful for ejecting someone from a
235site.
236<p>3. You can scan the sessions table to ensure no user
237can be logged in twice. Useful for security reasons.
238</p>
239<h3>Using Oracle CLOBs</h3>
240<p>Suppose you are storing the DATA field in a CLOB:
241 <pre><font color="#004040">
242   CREATE TABLE sessions (
243       SESSKEY VARCHAR(32) NOT NULL,
244       EXPIRY NUMBER(16)  NOT NULL,
245       EXPIREREF VARCHAR(64),
246       DATA CLOB,
247      PRIMARY KEY (sesskey)
248  );</font>
249 </pre>
250 <p>Then your PHP code could look like this:
251         <pre>
252        ADODB_SESSION_DRIVER='oci8';
253        $ADODB_SESSION_CONNECT=$tnsname;
254        $ADODB_SESSION_USER ='scott';
255        $ADODB_SESSION_PWD = 'tiger';
256        $ADODB_SESSION_DB ='';
257       
258        $ADODB_SESSION_USE_LOBS = 'clob';
259        $ADODB_SESSION_TBL = 'sessions';
260       
261        $ADODB_SESS_DEBUG=0;
262       
263        include(ADODB_DIR.'/session/adodb-session.php');
264       
265        ADODB_Session::persist('P'); # use 'C' for non-persistent connects
266       
267        session_start();
268 </pre>
269 <p>Note that you can set persistance using ADODB_Session::persist('P').
270 
271<h3>Compression/Encryption Schemes</h3>
272Since ADOdb 4.05, thanks to Ross Smith, multiple encryption and
273compression schemes are supported. Currently, supported are:
274<p>
275<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>
276<p>These are stackable. E.g.
277<p><pre>ADODB_Session::filter(new ADODB_Compress_Bzip2());<br>ADODB_Session::filter(new ADODB_Encrypt_MD5());<br></pre>
278will compress and then encrypt the record in the database.
279<h3>adodb_session_regenerate_id()</h3>
280<p>Dynamically change the current session id with a newly generated one and update database. Currently only
281works with cookies. Useful to improve security by reducing the risk of session-hijacking.
282See this article on <a href=http://shiflett.org/articles/security-corner-feb2004>Session Fixation</a> for more info
283on the theory behind this feature. Usage:
284<pre>
285        $ADODB_SESSION_DRIVER='mysql';
286        $ADODB_SESSION_CONNECT='localhost';
287        $ADODB_SESSION_USER ='root';
288        $ADODB_SESSION_PWD ='abc';
289        $ADODB_SESSION_DB ='phplens';
290       
291        include('path/to/adodb/session/adodb-session.php');
292       
293        session_start();
294        # Every 10 page loads, reset cookie for safety.
295        # This is extremely simplistic example, better
296        # to regenerate only when the user logs in or changes
297        # user privilege levels.
298        if ((rand()%10) == 0) adodb_session_regenerate_id();
299</pre>
300<p>This function calls session_regenerate_id() internally or simulates it if the function does not exist.
301<h3>Vacuum/Optimize Database</h3>
302<p>During session garbage collection, if postgresql is detected,
303  ADOdb can be set to run VACUUM. If mysql is detected, then optimize database
304  could be called.You can turn this on or off using:</p>
305<pre>$turnOn = true; # or false
306ADODB_Session::optimize($turnOn);
307</pre>
308<p>The default for optimization is it is disabled.</p>
309<h2>More Info</h2>
310<p>Also see the <a href="docs-adodb.htm">core ADOdb documentation</a>.
311</p>
312</body>
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