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22 | <h1>ADODB Session 2 Management Manual</h1> |
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23 | <p> |
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24 | V4.94 23 Jan 2007 (c) 2000-2007 John Lim (jlim#natsoft.com.my) |
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25 | </p> |
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26 | <p> <font size="1">This software is dual licensed using BSD-Style and |
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27 | LGPL. This means you can use it in compiled proprietary and commercial |
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28 | products. </font> |
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29 | <p>Useful ADOdb links: <a href="http://adodb.sourceforge.net/#download">Download</a> |
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30 | <a href="http://adodb.sourceforge.net/#docs">Other Docs</a> |
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31 | </p> |
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32 | <h2>Introduction</h2> |
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33 | <p> This document discusses the newer session handler adodb-session2.php. If |
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34 | you have used the older adodb-session.php, then be forewarned that you will |
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35 | need to alter your session table format. Otherwise everything is <a href="#compat">backward |
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36 | compatible</a>. |
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37 | Here are the <a href="docs-session.old.htm">older |
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38 | docs</a> for |
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39 | adodb-session.php.</p> |
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40 | <h2>Why Session Variables in a Database? </h2> |
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41 | <p>We store state information specific to a user or web |
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42 | client in session variables. These session variables persist throughout a |
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43 | session, as the user moves from page to page. </p> |
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44 | <p>To use session variables, call session_start() at the beginning of |
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45 | your web page, before your HTTP headers are sent. Then for every |
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46 | variable you want to keep alive for the duration of the session, call |
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47 | session_register($variable_name). By default, the session handler will |
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48 | keep track of the session by using a cookie. You can save objects or |
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49 | arrays in session variables also. |
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50 | </p> |
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51 | <p>The default method of storing sessions is to store it in a file. |
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52 | However if you have special needs such as you: |
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53 | </p> |
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54 | <ul> |
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55 | <li>Have multiple web servers that need to share session info</li> |
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56 | <li>Need to do special processing of each session</li> |
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57 | <li>Require notification when a session expires</li> |
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58 | </ul> |
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59 | <p>The ADOdb session handler provides you with the above |
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60 | additional capabilities by storing the session information as records |
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61 | in a database table that can be shared across multiple servers. </p> |
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62 | <p>These records will be garbage collected based on the php.ini [session] timeout settings. |
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63 | You can register a notification function to notify you when the record has expired and |
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64 | is about to be freed by the garbage collector.</p> |
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65 | <p>An alternative to using a database backed session handler is to use <a href="http://www.danga.com/memcached/">memcached</a>. |
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66 | This is a distributed memory based caching system suitable for storing session |
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67 | information. |
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68 | </p> |
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69 | <h2> The Improved Session Handler</h2> |
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70 | <p>In ADOdb 4.91, we added a new session handler, in adodb-session2.php. |
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71 | It features the following improvements: |
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72 | <ul> |
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73 | <li>Fully supports server farms using a new database table format. The |
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74 | previous version used the web server time for timestamps, which can cause problems |
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75 | on a system with multiple web servers with possibly inconsistent |
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76 | times. The new version uses the database server time instead for all timestamps. |
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77 | <li>The older database table format is obsolete. The database table must be modified |
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78 | to support storage of the database server time mentioned above. Also the field |
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79 | named DATA has been changed to SESSDATA. In some databases, DATA is a reserved |
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80 | word. |
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81 | <li>The functions dataFieldName() and syncSeconds() is obsolete. |
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82 | </ul> |
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83 | |
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84 | <p>Usage is |
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85 | |
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86 | <pre> |
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87 | include_once("adodb/session/adodb-session2.php"); |
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88 | ADOdb_Session::config($driver, $host, $user, $password, $database,$options=false); |
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89 | session_start(); |
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90 | |
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91 | <font |
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92 | color="#004040">#<br># Test session vars, the following should increment on refresh<br>#<br>$_SESSION['AVAR'] += 1;<br>print "<p>\$_SESSION['AVAR']={$_SESSION['AVAR']}</p>";</font> |
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93 | </pre> |
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94 | |
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95 | <p>When the session is created in session_start( ), the global variable $<b>ADODB_SESS_CONN</b> holds |
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96 | the connection object. |
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97 | <p>The default name of the table is sessions2. If you want to override it: |
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98 | |
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99 | <pre> |
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100 | include_once("adodb/session/adodb-session2.php"); |
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101 | $options['table'] = 'mytablename'; |
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102 | ADOdb_Session::config($driver, $host, $user, $password, $database,$options); |
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103 | session_start(); |
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104 | </pre> |
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105 | |
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106 | |
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107 | <h3>ADOdb Session Handler Features</h3> |
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108 | <ul> |
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109 | <li>Ability to define a notification function that is called when a |
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110 | session expires. Typically |
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111 | used to detect session logout and release global resources. </li> |
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112 | <li>Optimization of database writes. We crc32 the session data and |
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113 | only perform an update |
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114 | to the session data if there is a data change. </li> |
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115 | <li>Support for large amounts of session data with CLOBs (see |
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116 | adodb-session-clob2.php). Useful |
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117 | for Oracle. </li> |
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118 | <li>Support for encrypted session data, see |
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119 | adodb-cryptsession2.php. Enabling encryption is simply a matter of |
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120 | including adodb-cryptsession2.php instead of adodb-session2.php. </li> |
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121 | </ul> |
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122 | <h3>Session Handler Files </h3> |
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123 | <p>There are 3 session management files that you can use: |
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124 | </p> |
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125 | <pre>adodb-session2.php : The default<br>adodb-cryptsession2.php : Use this if you want to store encrypted session data in the database<br>adodb-session-clob2.php : Use this if you are storing DATA in clobs and you are NOT using oci8 driver</pre> |
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126 | <h2><strong>Usage Examples</strong></h2> |
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127 | <p>To force non-persistent connections, call <font color="#004040"><b>Persist</b></font>() first before session_start(): |
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128 | |
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129 | |
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130 | <pre> |
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131 | <font color="#004040"> |
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132 | include_once("adodb/session/adodb-session2.php"); |
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133 | $driver = 'mysql'; $host = 'localhost'; $user = 'auser'; $pwd = 'secret'; $database = 'sessiondb'; |
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134 | ADOdb_Session::config($driver, $host, $user, $password, $database,$options=false);<b><br>ADOdb_session::Persist($connectMode=false);</b> |
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135 | session_start();<br> </font> |
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136 | </pre> |
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137 | <p> The parameter to the Persist( ) method sets the connection mode. You can |
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138 | pass the following:</p> |
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139 | <table width="50%" border="1"> |
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140 | <tr> |
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141 | <td><b>$connectMode</b></td> |
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142 | <td><b>Connection Method</b></td> |
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143 | </tr> |
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144 | <tr> |
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145 | <td>true</td> |
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146 | <td><p>PConnect( )</p></td> |
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147 | </tr> |
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148 | <tr> |
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149 | <td>false</td> |
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150 | <td>Connect( )</td> |
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151 | </tr> |
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152 | <tr> |
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153 | <td>'N'</td> |
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154 | <td>NConnect( )</td> |
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155 | </tr> |
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156 | <tr> |
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157 | <td>'P'</td> |
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158 | <td>PConnect( )</td> |
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159 | </tr> |
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160 | <tr> |
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161 | <td>'C'</td> |
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162 | <td>Connect( )</td> |
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163 | </tr> |
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164 | </table> |
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165 | <p>To use a encrypted sessions, simply replace the file adodb-session2.php:</p> |
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166 | <pre> <font |
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167 | color="#004040"><b><br>include('adodb/session/adodb-cryptsession2.php');</b><br>$driver = 'mysql'; $host = 'localhost'; $user = 'auser'; $pwd = 'secret'; $database = 'sessiondb'; |
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168 | ADOdb_Session::config($driver, $host, $user, $password, $database,$options=false);<b><br>adodb_sess_open(false,false,$connectMode=false);</b> |
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169 | session_start();<br></font></pre> |
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170 | <p>And the same technique for adodb-session-clob2.php:</p> |
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171 | <pre> <font |
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172 | color="#004040"><br><b>include('adodb/session/adodb-session2-clob2.php');</b><br>$driver = 'oci8'; $host = 'localhost'; $user = 'auser'; $pwd = 'secret'; $database = 'sessiondb'; |
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173 | ADOdb_Session::config($driver, $host, $user, $password, $database,$options=false);<b><br>adodb_sess_open(false,false,$connectMode=false);</b> |
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174 | session_start();</font></pre> |
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175 | <h2>Installation</h2> |
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176 | <p>1. Create this table in your database. Here is the MySQL version: |
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177 | <pre> <a |
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178 | name="sessiontab"></a> <font color="#004040"> |
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179 | CREATE TABLE sessions2( |
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180 | sesskey VARCHAR( 64 ) NOT NULL DEFAULT '', |
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181 | expiry DATETIME NOT NULL , |
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182 | expireref VARCHAR( 250 ) DEFAULT '', |
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183 | created DATETIME NOT NULL , |
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184 | modified DATETIME NOT NULL , |
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185 | sessdata LONGTEXT DEFAULT '', |
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186 | PRIMARY KEY ( sesskey ) , |
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187 | INDEX sess2_expiry( expiry ), |
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188 | INDEX sess2_expireref( expireref ) |
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189 | )</font></pre> |
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190 | |
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191 | <p> For PostgreSQL, use: |
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192 | <pre>CREATE TABLE sessions2( |
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193 | sesskey VARCHAR( 64 ) NOT NULL DEFAULT '', |
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194 | expiry TIMESTAMP NOT NULL , |
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195 | expireref VARCHAR( 250 ) DEFAULT '', |
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196 | created TIMESTAMP NOT NULL , |
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197 | modified TIMESTAMP NOT NULL , |
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198 | sessdata TEXT DEFAULT '', |
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199 | PRIMARY KEY ( sesskey ) |
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200 | ); |
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201 | </pre> |
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202 | <pre>create INDEX sess2_expiry on sessions2( expiry ); |
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203 | create INDEX sess2_expireref on sessions2 ( expireref );</pre> |
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204 | <p>Here is the Oracle definition, which uses a CLOB for the SESSDATA field: |
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205 | <pre> |
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206 | <font |
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207 | color="#004040">CREATE TABLE SESSIONS2<br>(<br> SESSKEY VARCHAR2(48 BYTE) NOT NULL,<br> EXPIRY DATE NOT NULL,<br> EXPIREREF VARCHAR2(200 BYTE),<br> CREATED DATE NOT NULL,<br> MODIFIED DATE NOT NULL,<br> SESSDATA CLOB,<br> PRIMARY KEY(SESSKEY)<br>); |
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208 | <br>CREATE INDEX SESS2_EXPIRY ON SESSIONS2(EXPIRY); |
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209 | CREATE INDEX SESS2_EXPIREREF ON SESSIONS2(EXPIREREF);</font></pre> |
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210 | <p> We need to use a CLOB here because for text greater than 4000 bytes long, |
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211 | Oracle requires you to use the CLOB data type. If you are using the oci8 driver, |
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212 | ADOdb will automatically enable CLOB handling. So you can use either adodb-session2.php |
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213 | or adodb-session-clob2.php - in this case it doesn't matter. <br> |
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214 | <h2>Notifications</h2> |
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215 | <p>You can receive notification when your session is cleaned up by the session garbage collector or |
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216 | when you call session_destroy(). |
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217 | <p>PHP's session extension will automatically run a special garbage collection function based on |
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218 | your php.ini session.cookie_lifetime and session.gc_probability settings. This will in turn call |
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219 | adodb's garbage collection function, which can be setup to do notification. |
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220 | <p> |
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221 | <pre> |
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222 | PHP Session --> ADOdb Session --> Find all recs --> Send --> Delete queued |
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223 | GC Function GC Function to be deleted notification records |
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224 | executed at called by for all recs |
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225 | random time Session Extension queued for deletion |
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226 | </pre> |
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227 | <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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228 | the userid of the session. Later when the session has expired, just before the record is deleted, |
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229 | we reload the EXPIREREF field and call the notification function with the value of EXPIREREF, which |
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230 | is the userid of the person being logged off. |
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231 | <p>ADOdb uses a global variable $ADODB_SESSION_EXPIRE_NOTIFY that you must predefine before session |
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232 | start to store the notification configuration. |
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233 | $ADODB_SESSION_EXPIRE_NOTIFY is an array with 2 elements, the |
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234 | first being the name of the session variable you would like to store in |
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235 | the EXPIREREF field, and the 2nd is the notification function's name. </p> |
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236 | <p>For example, suppose we want to be notified when a user's session has expired, |
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237 | based on the userid. When the user logs in, we store the id in the global session variable |
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238 | $USERID. The function name is 'NotifyFn'. |
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239 | <p> |
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240 | So we define (before session_start() is called): </p> |
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241 | <pre> <font color="#004040"> |
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242 | $ADODB_SESSION_EXPIRE_NOTIFY = array('USERID','NotifyFn'); |
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243 | </font></pre> |
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244 | And when the NotifyFn is called (when the session expires), the |
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245 | $USERID is passed in as the first parameter, eg. NotifyFn($userid, $sesskey). The |
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246 | session key (which is the primary key of the record in the sessions |
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247 | table) is the 2nd parameter. |
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248 | <p> Here is an example of a Notification function that deletes some |
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249 | records in the database and temporary files: </p> |
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250 | <pre><font color="#004040"> |
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251 | function NotifyFn($expireref, $sesskey) |
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252 | { |
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253 | global $ADODB_SESS_CONN; # the session connection object |
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254 | $user = $ADODB_SESS_CONN->qstr($expireref); |
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255 | |
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256 | $ADODB_SESS_CONN->Execute("delete from shopping_cart where user=$user"); |
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257 | system("rm /work/tmpfiles/$expireref/*"); |
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258 | }</font> |
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259 | </pre> |
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260 | <p> NOTE 1: If you have register_globals disabled in php.ini, then you |
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261 | will have to manually set the EXPIREREF. E.g. </p> |
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262 | <pre> <font color="#004040"> |
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263 | $GLOBALS['USERID'] = GetUserID(); |
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264 | $ADODB_SESSION_EXPIRE_NOTIFY = array('USERID','NotifyFn');</font> |
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265 | </pre> |
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266 | <p> NOTE 2: If you want to change the EXPIREREF after the session |
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267 | record has been created, you will need to modify any session variable |
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268 | to force a database record update. |
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269 | </p> |
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270 | <h3>Neat Notification Tricks</h3> |
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271 | <p><i>ExpireRef</i> normally holds the user id of the current session. |
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272 | </p> |
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273 | <p>1. You can then write a session monitor, scanning expireref to see |
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274 | who is currently logged on. |
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275 | </p> |
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276 | <p>2. If you delete the sessions record for a specific user, eg. |
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277 | </p> |
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278 | <pre>delete from sessions where expireref = '$USER'<br></pre> |
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279 | then the user is logged out. Useful for ejecting someone from a |
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280 | site. |
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281 | <p>3. You can scan the sessions table to ensure no user |
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282 | can be logged in twice. Useful for security reasons. |
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283 | </p> |
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284 | <h2>Compression/Encryption Schemes</h2> |
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285 | Since ADOdb 4.05, thanks to Ross Smith, multiple encryption and |
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286 | compression schemes are supported. Currently, supported are: |
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287 | <p> |
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288 | <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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289 | <p>These are stackable. E.g. |
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290 | <pre>ADODB_Session::filter(new ADODB_Compress_Bzip2());<br>ADODB_Session::filter(new ADODB_Encrypt_MD5());<br></pre> |
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291 | will compress and then encrypt the record in the database. |
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292 | <h2>Session Cookie Regeneration: adodb_session_regenerate_id()</h2> |
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293 | <p>Dynamically change the current session id with a newly generated one and update |
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294 | database. Currently only works with cookies. Useful to improve security by |
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295 | reducing the risk of session-hijacking. See this article on <a href=http://shiflett.org/articles/security-corner-feb2004>Session |
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296 | Fixation</a> for more info |
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297 | on the theory behind this feature. Usage:<pre> |
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298 | include('path/to/adodb/session/adodb-session2.php'); |
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299 | |
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300 | session_start(); |
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301 | # Approximately every 10 page loads, reset cookie for safety. |
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302 | # This is extremely simplistic example, better |
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303 | # to regenerate only when the user logs in or changes |
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304 | # user privilege levels. |
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305 | if ((rand()%10) == 0) adodb_session_regenerate_id(); |
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306 | </pre> |
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307 | <p>This function calls session_regenerate_id() internally or simulates it if the function does not exist. |
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308 | <h2>Vacuum/Optimize Database</h2> |
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309 | <p>During session garbage collection, if postgresql is detected, |
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310 | ADOdb can be set to run VACUUM. If mysql is detected, then optimize database |
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311 | could be called.You can turn this on or off using:</p> |
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312 | <pre>$turnOn = true; # or false |
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313 | ADODB_Session::optimize($turnOn); |
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314 | </pre> |
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315 | <p>The default is optimization is disabled.</p> |
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316 | <h2><a name=compat></a>Backwards Compatability </h2> |
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317 | <p>The older method of connecting to ADOdb using global variables is still supported:</p> |
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318 | <pre> $ADODB_SESSION_DRIVER='mysql'; |
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319 | $ADODB_SESSION_CONNECT='localhost'; |
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320 | $ADODB_SESSION_USER ='root'; |
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321 | $ADODB_SESSION_PWD ='abc'; |
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322 | $ADODB_SESSION_DB ='phplens'; |
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323 | |
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324 | include('path/to/adodb/session/adodb-<strong>session2</strong>.php'); </pre> |
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325 | <p>In the above example, the only things you need to change in your code to upgrade |
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326 | is </p> |
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327 | <ul> |
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328 | <li>your session table format to the new one.</li> |
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329 | <li>the include file from adodb-session.php to adodb-session2.php. </li> |
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330 | </ul> |
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331 | <h2>More Info</h2> |
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332 | <p>Also see the <a href="docs-adodb.htm">core ADOdb documentation</a>. And if |
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333 | you are interested in the obsolete adodb-session.php, see <a href="docs-session.old.htm">old |
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334 | session documentation</a>. </p> |
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335 | </body> |
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336 | </html> |
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