SESSIONHANDLER(3)							 1							 SESSIONHANDLER(3)

The SessionHandler class

INTRODUCTION

       SessionHandler  is a special class that can be used to expose the current internal PHP session save handler by inheritance. There are seven
       methods which wrap the seven internal session save handler callbacks ($open, $close, $read, $write,  $destroy,  $gc  and  $create_sid).	By
       default, this class will wrap whatever internal save handler is set as defined by the session.save_handler configuration directive which is
       usually $files by default. Other internal session save handlers are provided by PHP extensions such as SQLite (as  $sqlite),  Memcache  (as
       $memcache), and Memcached (as $memcached).

	When  a  plain	instance of SessionHandler is set as the save handler using session_set_save_handler(3) it will wrap the current save han-
       dlers. A class extending from SessionHandler allows you to override the methods or intercept or filter them by calls the parent class meth-
       ods which ultimately wrap the interal PHP session handlers.

	This  allows  you,  for example, to intercept the $read and $write methods to encrypt/decrypt the session data and then pass the result to
       and from the parent class. Alternatively one might chose to entirely override a method like the garbage collection callback $gc.

	Because the SessionHandler wraps the current internal save handler methods, the above example of encryption can be applied to any internal
       save handler without having to know the internals of the handlers.

	To use this class, first set the save handler you wish to expose using session.save_handler and then pass an instance of SessionHandler or
       one extending it to session_set_save_handler(3).

	Please note the callback methods of this class are designed to be called internally by PHP and are not meant to be called from	user-space
       code.  The  return  values  are	equally  processed  internally	by  PHP.  For  more information on the session workflow, please refer ses-
       sion_set_save_handler(3).

CLASS SYNOPSIS

       SessionHandler

       SessionHandlerSessionHandlerInterface

       Methods

       o public bool SessionHandler::close (void  )

       o public string SessionHandler::create_sid (void  )

       o public bool SessionHandler::destroy (string  $session_id)

       o public bool SessionHandler::gc (int  $maxlifetime)

       o public bool SessionHandler::open (string  $save_path, string  $session_name)

       o public string SessionHandler::read (string  $session_id)

       o public bool SessionHandler::write (string  $session_id, string  $session_data)

       Warning

	       This class is designed to expose the current internal PHP session save handler, if you want to write your own custom save handlers,
	      please implement the SessionHandlerInterface interface instead of extending from SessionHandler.

CHANGELOG

       +--------+--------------------------------------+
       |Version |				       |
       |	|				       |
       |	|	      Description	       |
       |	|				       |
       +--------+--------------------------------------+
       | 5.5.1	|				       |
       |	|				       |
       |	|  Added SessionHandler.create_sid(3). |
       |	|				       |
       +--------+--------------------------------------+
       Example #1

	       Using SessionHandler to add encryption to internal PHP save handlers.

	      <?php
	      class EncryptedSessionHandler extends SessionHandler
	      {
		  private $key;

		  public function __construct($key)
		  {
		      $this->key = $key;
		  }

		  public function read($id)
		  {
		      $data = parent::read($id);

		      return mcrypt_decrypt(MCRYPT_3DES, $this->key, $data, MCRYPT_MODE_ECB);
		  }

		  public function write($id, $data)
		  {
		      $data = mcrypt_encrypt(MCRYPT_3DES, $this->key, $data, MCRYPT_MODE_ECB);

		      return parent::write($id, $data);
		  }
	      }

	      // we'll intercept the native 'files' handler, but will equally work
	      // with other internal native handlers like 'sqlite', 'memcache' or 'memcached'
	      // which are provided by PHP extensions.
	      ini_set('session.save_handler', 'files');
	      $handler = new EncryptedSessionHandler('mykey');
	      session_set_save_handler($handler, true);
	      session_start();

	      // proceed to set and retrieve values by key from $_SESSION

       Note

	       Since  this class' methods are designed to be called internally by PHP as part of the normal session workflow, child class calls to
	      parent methods (i.e. the actual internal native handlers) will return FALSE unless the session has  actually  been  started  (either
	      automatically,  or by explicit session_start(3). This is important to consider when writing unit tests where the class methods might
	      be invoked manually.

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