1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
|
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html>
<head>
<title>Code Igniter User Guide</title>
<style type='text/css' media='all'>@import url('../userguide.css');</style>
<link rel='stylesheet' type='text/css' media='all' href='../userguide.css' />
<script type="text/javascript" src="../scripts/nav.js"></script>
<script type="text/javascript" src="../scripts/prototype.lite.js"></script>
<script type="text/javascript" src="../scripts/moo.fx.js"></script>
<script type="text/javascript">
window.onload = function() {
myHeight = new fx.Height('nav', {duration: 400});
myHeight.hide();
}
</script>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<meta http-equiv='expires' content='-1' />
<meta http-equiv= 'pragma' content='no-cache' />
<meta name='robots' content='all' />
<meta name='author' content='Rick Ellis' />
<meta name='description' content='Code Igniter User Guide' />
</head>
<body>
<!-- START NAVIGATION -->
<div id="nav"><div id="nav_inner"><script type="text/javascript">create_menu('../');</script></div></div>
<div id="nav2"><a name="top"></a><a href="javascript:void(0);" onclick="myHeight.toggle();"><img src="../images/nav_toggle.jpg" width="153" height="44" border="0" title="Toggle Table of Contents" alt="Toggle Table of Contents" /></a></div>
<div id="masthead">
<table cellpadding="0" cellspacing="0" border="0" style="width:100%">
<tr>
<td><h1>Code Igniter User Guide Version 1.4.0</h1></td>
<td id="breadcrumb_right"><a href="../toc.html">Full Table of Contents</a></td>
</tr>
</table>
</div>
<!-- END NAVIGATION -->
<!-- START BREADCRUMB -->
<table cellpadding="0" cellspacing="0" border="0" style="width:100%">
<tr>
<td id="breadcrumb">
<a href="http://www.codeigniter.com/">Code Igniter Home</a> ›
<a href="../index.html">User Guide Home</a> ›
Session Class
</td>
<td id="searchbox"><form method="get" action="http://www.google.com/search"><input type="hidden" name="as_sitesearch" id="as_sitesearch" value="www.codeigniter.com/user_guide/" />Search User Guide <input type="text" class="input" style="width:200px;" name="q" id="q" size="31" maxlength="255" value="" /> <input type="submit" class="submit" name="sa" value="Go" /></form></td>
</tr>
</table>
<!-- END BREADCRUMB -->
<br clear="all" />
<!-- START CONTENT -->
<div id="content">
<h1>Session Class</h1>
<p>The Session class permits you maintain a user's "state" and track their activity while they browse your site.
The Session class stores session information for each user as serialized (and optionally encrypted) data in a cookie.
It can also store the session data in a database table for added security, as this permits the session ID in the
user's cookie to be matched against the stored session ID. By default only the cookie is saved. If you choose to
use the database option you'll need to create the session table as indicated below.
</p>
<p class="important"><strong>Note:</strong> The Session class does <strong>not</strong> utilize native PHP sessions. It
generates its own session data, offering more flexibility for developers.</p>
<h2>Initializing a Session</h2>
<p>Sessions will typically run globally with each page load, so the session class must either be
<a href="../general/libraries.html">initialized</a> in your
<a href="../general/controllers.html">controller</a> constructors, or it can be
<a href="../general/autoloader.html">auto-loaded</a> by the system.
For the most part the session class will run unattended in the background, so simply initializing the class
will cause it to read, create, and update sessions.</p>
<p>To initialize the Session class manually in your controller constructor, use the <dfn>$this->load->library</dfn> function:</p>
<code>$this->load->library('session');</code>
<p>Once loaded, the Sessions library object will be available using: <dfn>$this->session</dfn></p>
<h2>How do Sessions work?</h2>
<p>When a page is loaded, the session class will check to see if valid session data exists in the user's session cookie.
If sessions data does <strong>not</strong> exist (or if it has expired) a new session will be created and saved in the cookie.
If a session does exist, its information will be updated and the cookie will be updated.</p>
<p>It's important for you to understand that once initialized, the Session class runs automatically. There is nothing
you need to do to cause the above behavior to happen. You can, as you'll see below, work with session data or
even add your own data to a user's session, but the process of reading, writing, and updating a session is automatic.</p>
<h2>What is Session Data?</h2>
<p>A <em>session</em>, as far as Code Igniter is concerned, is simply an array containing the following information:</p>
<ul>
<li>The user's unique Session ID (this is a statistically random string with very strong entropy, hashed with MD5 for portability)</li>
<li>The user's IP Address</li>
<li>The user's User Agent data (the first 50 characters of the browser data string)</li>
<li>The "last activity" and "last visit" time stamps.</li>
</ul>
<p>The above data is stored in a cookie as a serialized array with this prototype:</p>
<code>[array]<br />
(<br />
'session_id' => random hash,<br />
'ip_address' => 'string - user IP address',<br />
'user_agent' => 'string - user agent data',<br />
'last_activity' => timestamp,<br />
'last_visit' => timestamp<br />
)</code>
<p>If you have the encryption option enabled, the serialized array will be encrypted before being stored in the cookie,
making the data highly secure and impervious to being read or altered by someone. More info regarding encryption
can be <a href="encryption.html">found here</a>, although the Session class will take care of initializing
and encrypting the data automatically.</p>
<p>Note: Session cookies are only updated every five minutes to reduce processor load. If you repeatedly reload a page
you'll notice that the "last activity" time only updates if five minutes or more has passed since the last time
the cookie was written.</p>
<h2>Retrieving Session Data</h2>
<p>Any piece of information from the session array is available using the following function:</p>
<code>$this->session->userdata('<samp>item</samp>');</code>
<p>Where <samp>item</samp> is the array index corresponding to the item you wish to fetch. For example, to fetch the session ID you
will do this:</p>
<code>$session_id = $this->session->userdata('<samp>session_id</samp>');</code>
<p><strong>Note:</strong> The function returns FALSE (boolean) if the item you are trying to access does not exist.</p>
<h2>Adding Custom Session Data</h2>
<p>A useful aspect of the session array is that you can add your own data to it and it will be stored in the user's cookie.
Why would you want to do this? Here's one example:</p>
<p>Let's say a particular user logs into your site. Once authenticated,
you could add their username and email address to the session cookie, making that data globally available to you without
having to run a database query when you need it.</p>
<p>To add your data to the session array involves passing an array containing your new data to this function:</p>
<code>$this->session->set_userdata(<samp>$array</samp>);</code>
<p>Where <samp>$array</samp> is an associative array containing your new data. Here's an example:</p>
<code>$newdata = array(<br />
'username' => 'johndoe',<br />
'email' => 'johndoe@some-site.com',<br />
'logged_in' => TRUE<br />
);<br />
<br />
$this->session->set_userdata(<samp>$newdata</samp>);</code>
<p class="important"><strong>Note:</strong> Cookies can only hold 4KB of data, so be careful not to exceed the capacity. The
encryption process in particular produces a longer data string than the original so keep careful track of how much data you are storing.</p>
<h2>Saving Session Data to a Database</h2>
<p>While the session data array stored in the user's cookie contains a Session ID,
unless you store session data in a database there is no way to validate it. For some applications that require little or no
security, session ID validation may not be needed, but if your application requires security, validation is mandatory.</p>
<p>When session data is available in a database, every time a valid session is found in the user's cookie, a database
query is performed to match it. If the session ID does not match, the session is destroyed. Session IDs can never
be updated, they can only be generated when a new session is created.</p>
<p>In order to store sessions, you must first create a database table for this purpose. Here is the basic
prototype required by the session class:</p>
<textarea class="textarea" style="width:100%" cols="50" rows="8">
CREATE TABLE IF NOT EXISTS `ci_sessions` (
session_id varchar(40) DEFAULT '0' NOT NULL,
ip_address varchar(16) DEFAULT '0' NOT NULL,
user_agent varchar(50) NOT NULL,
last_activity int(10) unsigned DEFAULT 0 NOT NULL,
PRIMARY KEY (session_id)
);</textarea>
<p><strong>Note:</strong> By default the table is called <dfn>ci_sessions</dfn>, but you can name it anything you want
as long as you update the <kbd>application/config/config.php</kbd> file so that it contains the name you have chosen.
Once you have created your database table you can enable the database option in your config.php file as follows:</p>
<code>$config['sess_use_database'] = TRUE;</code>
<p>Once enabled, the Session class will store session data in the DB.</p>
<h2>Session Preferences</h2>
<p>You'll find the following Session related preferences in your <kbd>application/config/config.php</kbd> file:</p>
<table cellpadding="0" cellspacing="1" border="0" style="width:100%" class="tableborder">
<tr>
<th>Preference</th>
<th>Default</th>
<th>Options</th>
<th>Description</th>
</tr><tr>
<td class="td"><strong>sess_cookie_name</strong></td>
<td class="td">ci_session</td
><td class="td">None</td>
<td class="td">The name you world the session cookie saved as.</td>
</tr><tr>
<td class="td"><strong>sess_expiration</strong></td>
<td class="td">7200</td>
<td class="td">None</td>
<td class="td">The number of seconds you would like the session to last. The default value is 2 hours (7200 seconds).
If you would like a non-expiring session set the value to zero: 0</td>
</tr><tr>
<td class="td"><strong>sess_encrypt_cookie</strong></td>
<td class="td">TRUE</td>
<td class="td">TRUE/FALSE (boolean)</td>
<td class="td">Whether to encrypt the session data.</td>
</tr><tr>
<td class="td"><strong>sess_use_database</strong></td>
<td class="td">FALSE</td>
<td class="td">TRUE/FALSE (boolean)</td>
<td class="td">Whether to save the session data to a database. You must create the table before enabling this option.</td>
</tr><tr>
<td class="td"><strong>sess_table_name</strong></td>
<td class="td">ci_sessions</td
><td class="td">Any valid SQL table name</td>
<td class="td">The name of the session database table.</td>
</tr><tr>
<td class="td"><strong>sess_match_ip</strong></td>
<td class="td">FALSE</td>
<td class="td">TRUE/FALSE (boolean)</td>
<td class="td">Whether to match the user's IP address when reading the session data. Note that some ISPs dynamically
changes the IP, so if you want a non-expiring session you will likely set this to FALSE.</td>
</tr><tr>
<td class="td"><strong>sess_match_useragent</strong></td>
<td class="td">TRUE</td>
<td class="td">TRUE/FALSE (boolean)</td>
<td class="td">Whether to match the User Agent when reading the session data.</td>
</tr>
</table>
</div>
<!-- END CONTENT -->
<div id="footer">
<p>
Previous Topic: <a href="pagination.html">Pagination Class</a>
·
<a href="#top">Top of Page</a> ·
<a href="../index.html">User Guide Home</a> ·
Next Topic: <a href="trackback.html">Trackback Class</a>
<p>
<p><a href="http://www.codeigniter.com">Code Igniter</a> · Copyright © 2006 · <a href="http://www.pmachine.com">pMachine, Inc.</a></p>
</div>
</body>
</html>
|
