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22 <h3>ADODB Session Management Manual</h3>
23 <p>
24 V4.94 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
27 LGPL. This means you can use it in compiled proprietary and commercial
28 products. </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.
34 Here 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
36 session variables. These session variables persist throughout a
37 session, as the user moves from page to page. </p>
38 <p>To use session variables, call session_start() at the beginning of
39 your web page, before your HTTP headers are sent. Then for every
40 variable you want to keep alive for the duration of the session, call
41 session_register($variable_name). By default, the session handler will
42 keep track of the session by using a cookie. You can save objects or
43 arrays in session variables also.
44 </p>
45 <p>The default method of storing sessions is to store it in a file.
46 However 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
54 additional capabilities by storing the session information as records
55 in 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.
57 You can register a notification function to notify you when the record has expired and
58 is about to be freed by the garbage collector.</p>
59 <p><b>Important Upgrade Notice:</b> Since ADOdb 4.05, the session files
60 have been moved to its own folder, adodb/session. This is a rewrite
61 of the session code by Ross Smith. The old session code is in
62 adodb/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
66 session expires. Typically
67 used to detect session logout and release global resources. </li>
68 <li>Optimization of database writes. We crc32 the session data and
69 only perform an update
70 to the session data if there is a data change. </li>
71 <li>Support for large amounts of session data with CLOBs (see
72 adodb-session-clob.php). Useful
73 for Oracle. </li>
74 <li>Support for encrypted session data, see
75 adodb-cryptsession.php. Enabling encryption is simply a matter of
76 including 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>
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>
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
171 when you call session_destroy().
172 <p>PHP's session extension will automatically run a special garbage collection function based on
173 your php.ini session.cookie_lifetime and session.gc_probability settings. This will in turn call
174 adodb'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
183 the userid of the session. Later when the session has expired, just before the record is deleted,
184 we reload the EXPIREREF field and call the notification function with the value of EXPIREREF, which
185 is 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
187 start to store the notification configuration.
188 $ADODB_SESSION_EXPIRE_NOTIFY is an array with 2 elements, the
189 first being the name of the session variable you would like to store in
190 the 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,
192 based 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>
195 So we define (before session_start() is called): </p>
196 <pre> <font color="#004040">
198 </font></pre>
199 And when the NotifyFn is called (when the session expires), the
200 $USERID is passed in as the first parameter, eg. NotifyFn($userid, $sesskey). The
201 session key (which is the primary key of the record in the sessions
202 table) is the 2nd parameter.
203 <p> Here is an example of a Notification function that deletes some
204 records in the database and temporary files: </p>
205 <pre><font color="#004040">
206 function NotifyFn($expireref, $sesskey)
207 {
208 global $ADODB_SESS_CONN; # the session connection object
209 $user = $ADODB_SESS_CONN-&gt;qstr($expireref);
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
216 will have to manually set the EXPIREREF. E.g. </p>
217 <pre> <font color="#004040">
218 $GLOBALS['USERID'] = GetUserID();
219 $ADODB_SESSION_EXPIRE_NOTIFY = array('USERID','NotifyFn');</font>
220 </pre>
221 <p> NOTE 2: If you want to change the EXPIREREF after the session
222 record has been created, you will need to modify any session variable
223 to force a database record update.
224 </p>
225 <h4>Neat Notification Tricks</h4>
226 <p><i>ExpireRef</i> normally holds the user id of the current session.
227 </p>
228 <p>1. You can then write a session monitor, scanning expireref to see
229 who is currently logged on.
230 </p>
231 <p>2. If you delete the sessions record for a specific user, eg.
232 </p>
233 <pre>delete from sessions where expireref = '$USER'<br></pre>
234 then the user is logged out. Useful for ejecting someone from a
235 site.
236 <p>3. You can scan the sessions table to ensure no user
237 can 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 (
247 PRIMARY KEY (sesskey)
248 );</font>
249 </pre>
250 <p>Then your PHP code could look like this:
251 <pre>
254 $ADODB_SESSION_USER ='scott';
255 $ADODB_SESSION_PWD = 'tiger';
259 $ADODB_SESSION_TBL = 'sessions';
263 include(ADODB_DIR.'/session/adodb-session.php');
265 ADODB_Session::persist('P'); # use 'C' for non-persistent connects
267 session_start();
268 </pre>
269 <p>Note that you can set persistance using ADODB_Session::persist('P').
271 <h3>Compression/Encryption Schemes</h3>
272 Since ADOdb 4.05, thanks to Ross Smith, multiple encryption and
273 compression 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>
278 will 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
281 works with cookies. Useful to improve security by reducing the risk of session-hijacking.
282 See this article on <a href=http://shiflett.org/articles/security-corner-feb2004>Session Fixation</a> for more info
283 on the theory behind this feature. Usage:
284 <pre>
286 $ADODB_SESSION_CONNECT='localhost';
287 $ADODB_SESSION_USER ='root';
288 $ADODB_SESSION_PWD ='abc';
289 $ADODB_SESSION_DB ='phplens';
291 include('path/to/adodb/session/adodb-session.php');
293 session_start();
294 # Every 10 page loads, reset cookie for safety.
295 # This is extremely simplistic example, better
296 # to regenerate only when the user logs in or changes
297 # user privilege levels.
298 if ((rand()%10) == 0) adodb_session_regenerate_id();
299 </pre>
300 <p>This function calls session_regenerate_id() internally or simulates it if the function does not exist.
301 <h3>Vacuum/Optimize Database</h3>
302 <p>During session garbage collection, if postgresql is detected,
303 ADOdb can be set to run VACUUM. If mysql is detected, then optimize database
304 could be called.You can turn this on or off using:</p>
305 <pre>$turnOn = true; # or false
306 ADODB_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>
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