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   1  <?php
   2  /**
   3   *  File containing the Session class
   4   *
   5   *  (PHP 5)
   6   *
   7   *  @package PHPonTrax
   8   *  @version $Id: session.php 248 2006-08-23 06:24:54Z john $
   9   *  @copyright (c) 2005 John Peterson
  10   *
  11   *  Permission is hereby granted, free of charge, to any person obtaining
  12   *  a copy of this software and associated documentation files (the
  13   *  "Software"), to deal in the Software without restriction, including
  14   *  without limitation the rights to use, copy, modify, merge, publish,
  15   *  distribute, sublicense, and/or sell copies of the Software, and to
  16   *  permit persons to whom the Software is furnished to do so, subject to
  17   *  the following conditions:
  18   *
  19   *  The above copyright notice and this permission notice shall be
  20   *  included in all copies or substantial portions of the Software.
  21   *
  22   *  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  23   *  EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  24   *  MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  25   *  NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
  26   *  LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
  27   *  OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
  28   *  WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  29   */
  30  
  31  /**
  32   *  Keep track of state of the client's session with the server
  33   *
  34   *  Since there is no continuous connection between the client and the
  35   *  web server, there must be some way to carry information forward
  36   *  from one page to the next.  PHP does this with a global array variable
  37   *  {@link http://www.php.net/manual/en/reserved.variables.php#reserved.variables.session $_SESSION}
  38   *  which is automatically restored from an area of the server's hard disk
  39   *  indicated by the contents of a cookie stored on the client's computer.
  40   *  This class is a static class with convenience methods for accessing the 
  41   *  contents of $_SESSION.
  42   *   @tutorial PHPonTrax/Session.cls
  43   */
  44  class Session {
  45  
  46      /**
  47       *  Name of the session (used as cookie name).
  48       */
  49      const TRAX_SESSION_NAME = "TRAXSESSID";
  50  
  51      /**
  52       *  Lifetime in seconds of cookie or, if 0, until browser is restarted.
  53       */
  54      const TRAX_SESSION_LIFETIME = "0";
  55  
  56      /**
  57       *  After this number of minutes, stored data will be seen as
  58       *  'garbage' and cleaned up by the garbage collection process.
  59       */
  60      const TRAX_SESSION_MAXLIFETIME_MINUTES = "20";
  61  
  62      /**
  63       *  IP Address of client
  64       *  @var string
  65       */
  66      private static $ip = null;
  67  
  68      /**
  69       *  User Agent (OS, Browser, etc) of client
  70       *  @var string
  71       */
  72      private static $user_agent = null;
  73  
  74      /**
  75       *  Session started
  76       *  @var boolean
  77       */
  78      private static $started = false;  
  79  
  80      /**
  81       *  Session ID
  82       *  @var string
  83       */
  84      public static $id = null;
  85      
  86      /**
  87       *  Get a session variable
  88       *
  89       *  Fetch the contents from a specified element of
  90       *  {@link http://www.php.net/manual/en/reserved.variables.php#reserved.variables.session $_SESSION}
  91       *  @param mixed $key Key to identify one particular session variable
  92       *                    of potentially many for this session
  93       *  @return mixed Content of the session variable with the specified
  94       *                key if the variable exists; otherwise null.
  95       *  @uses get_hash()
  96       *  @uses is_valid_host()
  97       */
  98      function get($key) {
  99          if(self::is_valid_host()) {
 100              return $_SESSION[self::get_hash()][$key];
 101          }
 102          return null;
 103      }
 104  
 105      /**
 106       *  Set a session variable
 107       *
 108       *  Store a value in a specified element of
 109       *  {@link http://www.php.net/manual/en/reserved.variables.php#reserved.variables.session $_SESSION}
 110       *  @param mixed $key Key to identify one particular session variable
 111       *                    of potentially many for this session
 112       *  @param string $value Value to store in the session variable
 113       *                       identified by $key  
 114       *  @uses get_hash()
 115       *  @uses is_valid_host()
 116       *  
 117       */
 118      function set($key, $value) {
 119          if(self::is_valid_host()) {
 120              $_SESSION[self::get_hash()][$key] = $value;
 121          }
 122       }
 123  
 124      /**
 125       *  Test whether the user host is as expected for this session
 126       *
 127       *  Compare the REMOTE_ADDR and HTTP_USER_AGENT elements of 
 128       *  {@link http://www.php.net/manual/en/reserved.variables.php#reserved.variables.server $_SERVER}
 129       *  to the expected values for this session.
 130       *  @uses $ip
 131       *  @uses is_aol_host()
 132       *  @uses $user_agent
 133       *  @return boolean
 134       *          <ul>
 135       *            <li>true =>  User host is as expected</li>
 136       *            <li>false => User host NOT as expected</li>
 137       *          </ul>
 138       */
 139      function is_valid_host() {
 140          if(($_SERVER['REMOTE_ADDR'] == self::$ip || self::is_aol_host()) &&
 141             $_SERVER['HTTP_USER_AGENT'] == self::$user_agent) {
 142              return true;
 143          }
 144          return false;
 145      }
 146  
 147      /**
 148       *  Test whether the client is an AOL user
 149       *
 150       *  Check whether the domain name of the client's IP ends in
 151       *  "proxy.aol.com" or the client's user agent name includes "AOL"
 152       *  @return boolean
 153       *          <ul>
 154       *            <li>true =>  Client is on AOL</li>
 155       *            <li>false => Client from some other ISP</li>
 156       *          </ul>
 157       */
 158      function is_aol_host() {
 159          if(ereg("proxy\.aol\.com$", gethostbyaddr($_SERVER['REMOTE_ADDR'])) ||
 160             stristr($_SERVER['HTTP_USER_AGENT'], "AOL")) {
 161              return true;
 162          }
 163          return false;
 164      }
 165  
 166      /**
 167       *  Get key that uniquely identifies this session
 168       *
 169       *  Calculate a unique session key based on the session ID and
 170       *  user agent, plus the user's IP address if not on AOL.
 171       *  @uses is_aol_host()
 172       *  @uses md5()
 173       *  @uses session_id()
 174       */
 175      function get_hash() {
 176          $key = session_id().$_SERVER['HTTP_USER_AGENT'];
 177          if(!self::is_aol_host()) {
 178              $key .= $_SERVER['REMOTE_ADDR'];
 179          }
 180          // error_log('get_hash() returns '.md5($key));
 181          return md5($key);
 182      }
 183  
 184      /**
 185       *  Start or continue a session
 186       *
 187       *  @uses ini_set()
 188       *  @uses $ip
 189       *  @uses is_valid_host()
 190       *  @uses session_id()
 191       *  @uses session_start()
 192       *  @uses $user_agent
 193       */
 194      function start() {
 195          
 196          if(!self::$started) {
 197              $session_name = defined("TRAX_SESSION_NAME") ? TRAX_SESSION_NAME : self::TRAX_SESSION_NAME;
 198              $session_lifetime = defined("TRAX_SESSION_LIFETIME") ? TRAX_SESSION_LIFETIME : self::TRAX_SESSION_LIFETIME;
 199              $session_maxlifetime_minutes = defined("TRAX_SESSION_MAXLIFETIME_MINUTES") ? TRAX_SESSION_MAXLIFETIME_MINUTES : self::TRAX_SESSION_MAXLIFETIME_MINUTES;
 200              
 201              # set the session default for this app
 202              ini_set('session.name', $session_name);
 203              ini_set('session.cookie_lifetime', $session_lifetime);
 204              ini_set('session.gc_probability', 1);
 205              ini_set('session.gc_maxlifetime', $session_maxlifetime_minutes * 60);
 206      
 207              header('P3P: CP="NOI ADM DEV PSAi COM NAV OUR OTRo STP IND DEM"');
 208      
 209              self::$ip = $_SERVER['REMOTE_ADDR'];
 210              self::$user_agent = $_SERVER['HTTP_USER_AGENT'];
 211      
 212              if(self::is_valid_host() && array_key_exists('sess_id',$_REQUEST)) {
 213                  session_id($_REQUEST['sess_id']);
 214              }
 215      
 216              session_cache_limiter("must-revalidate");
 217              session_start();
 218              self::$id = session_id();
 219              self::$started = true;
 220          }
 221      }
 222  
 223      /**
 224       *  Destroy the user's session
 225       *
 226       *  Destroy all data registered to a session
 227       *
 228       *  @uses session_destroy()
 229       */
 230      function destory_session() {
 231          session_destroy();
 232      }
 233  
 234      /**
 235       *  Free all session variables currently registered
 236       *
 237       *  @uses get_hash()
 238       *  @uses session_unset()
 239       */
 240      function unset_session() {
 241          session_unset($_SESSION[self::get_hash()]);
 242      }
 243  
 244      /**
 245       *  Unset a session variable
 246       *
 247       *  Unset the variable in 
 248       *  {@link http://www.php.net/manual/en/reserved.variables.php#reserved.variables.session $_SESSION}
 249       *  identified by key $key
 250       *  @uses get_hash()
 251       *  @uses is_valid_host()
 252       */
 253      function unset_var($key) {
 254           // error_log('Session::unset_var("'.$key.'")');
 255          if(self::is_valid_host()) {
 256              // error_log('before unsetting SESSION='.var_export($_SESSION,true));
 257              unset($_SESSION[self::get_hash()][$key]);
 258              // error_log('after unsetting SESSION='.var_export($_SESSION,true));
 259          }
 260      }
 261  
 262      /**
 263       *  Test whether a session variable is defined in $_SESSION
 264       *
 265       *  Check the 
 266       *  {@link http://www.php.net/manual/en/reserved.variables.php#reserved.variables.session $_SESSION}
 267       *  array for the existance of a variable identified by $key
 268       *  @param mixed $key Key to identify one particular session variable
 269       *                    of potentially many for this session
 270       *  @return boolean
 271       *          <ul>
 272       *            <li>true =>  The specified session variable is
 273       *                         defined.</li>
 274       *            <li>false => The specified session variable is
 275       *                         not defined.</li>
 276       *          </ul>
 277       *  @uses get_hash()
 278       *  @uses is_valid_host()
 279       */
 280      function isset_var($key) {
 281          if(self::is_valid_host()) {
 282              if($_SESSION[self::get_hash()][$key]) {
 283                  return true;    
 284              }
 285          }
 286          return false;
 287      }
 288  
 289      /**
 290       *  Test whether there is a flash message to be shown
 291       *
 292       *  Check whether the
 293       *  {@link http://www.php.net/manual/en/reserved.variables.php#reserved.variables.session $_SESSION}
 294       *  array for this session contains a
 295       *  flash message to be shown to the user.
 296       *  @param mixed $key Key to identify one particular flash message
 297       *                    of potentially many for this session
 298       *  @return boolean
 299       *          <ul>
 300       *            <li>true =>  A flash message is present</li>
 301       *            <li>false => No flash message is present</li>
 302       *          </ul>
 303       *  @uses get_hash()
 304       *  @uses is_valid_host()
 305       */
 306      function isset_flash($key) {
 307          if(self::is_valid_host()) {
 308              if(array_key_exists(self::get_hash(), $_SESSION)
 309                 && array_key_exists('flash',$_SESSION[self::get_hash()])
 310                 && array_key_exists($key,
 311                                     $_SESSION[self::get_hash()]['flash'])) {
 312                  return true;    
 313              }
 314          }
 315          return false;
 316      }
 317  
 318      /**
 319       *  Get or set a flash message
 320       *
 321       *  A flash message is a message that will appear prominently on
 322       *  the next screen to be sent to the user. Flash
 323       *  messages are intended to be shown to the user once then erased. 
 324       *  They are stored in the
 325       *  {@link http://www.php.net/manual/en/reserved.variables.php#reserved.variables.session $_SESSION}
 326       *  array for the user's session.
 327       *
 328       *  @param mixed $key Key to identify one particular flash message
 329       *                    of potentially many for this session
 330       *  @param string $value Content of the flash message if present
 331       *  @return mixed Content of the flash message with the specified
 332       *                key if $value is null; otherwise null.
 333       *  @uses get_hash()
 334       *  @uses is_valid_host()
 335       */
 336      function flash($key, $value = null) {
 337          if(self::is_valid_host()) {
 338              if($value) {
 339                  $_SESSION[self::get_hash()]['flash'][$key] = $value;
 340              } else {
 341                  $value = $_SESSION[self::get_hash()]['flash'][$key];
 342                  unset($_SESSION[self::get_hash()]['flash'][$key]);
 343                  return $value;
 344              }
 345          }
 346      }
 347  }
 348  
 349  // -- set Emacs parameters --
 350  // Local variables:
 351  // tab-width: 4
 352  // c-basic-offset: 4
 353  // c-hanging-comment-ender-p: nil
 354  // indent-tabs-mode: nil
 355  // End:
 356  ?>