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CGI::Session(3) 	       User Contributed Perl Documentation		  CGI::Session(3)

NAME
       CGI::Session - persistent session data in CGI applications

SYNOPSIS
	   # Object initialization:
	   use CGI::Session;
	   $session = new CGI::Session();

	   $CGISESSID = $session->id();

	   # Send proper HTTP header with cookies:
	   print $session->header();

	   # Storing data in the session:
	   $session->param('f_name', 'Sherzod');
	   # or
	   $session->param(-name=>'l_name', -value=>'Ruzmetov');

	   # Flush the data from memory to the storage driver at least before your
	   # program finishes since auto-flushing can be unreliable.
	   # Warning: A bug in your logic whereby the DBI handle has gone
	   # out of scope before flush() is called means flush() won't work
	   # (when the session is a database session), so don't do that.
	   $session->flush();

	   # Retrieving data:
	   my $f_name = $session->param('f_name');
	   # or
	   my $l_name = $session->param(-name=>'l_name');

	   # Clearing a certain session parameter:
	   $session->clear(["l_name", "f_name"]);

	   # Expire '_is_logged_in' flag after 10 idle minutes:
	   $session->expire('is_logged_in', '+10m')

	   # Expire the session itself after 1 idle hour:
	   $session->expire('+1h');

	   # Delete the session for good:
	   $session->delete();
	   $session->flush(); # Recommended practice says use flush() after delete().

DESCRIPTION
       CGI-Session is a Perl5 library that provides an easy, reliable and modular session
       management system across HTTP requests.	Persistency is a key feature for such
       applications as shopping carts, login/authentication routines, and application that need
       to carry data across HTTP requests. CGI::Session does that and many more.

A Warning about Auto-flushing
       As mentioned above in the Synopsis, auto-flushing can be unreliable.

       Consequently, you should regard it as mandatory that sessions always need to be explicitly
       flushed before the program exits.

       For instance, in a "CGI::Application"-based program, "sub teardown()" would be the
       appropriate place to do this.

       This is all part of what might be called "Object life-cycle 'v' Program life-cycle".

       In the simplest case the program has one object of type CGI::Session, and that object is
       destroyed when the program exits.

       If, however, you wish to delete objects explicitly, then each call to "delete()" should be
       followed by a call to "flush()".

       Warning: A bug in your logic whereby the DBI handle has gone out out of scope before
       flush() is called means flush() won't work (when the session is a database session), so
       don't do that.

       For more detail, see the discussion of the "delete()" method, below.

A Warning about UTF8
       Trying to use UTF8 in a program which uses CGI::Session has lead to problems. See RT#21981
       and RT#28516.

       In the first case the user tried "use encoding 'utf8';" in the program, and in the second
       case the user tried "$dbh->do(qq|set names 'utf8'|);".

       Until this problem is understood and corrected, users are advised to avoid UTF8 in
       conjunction with CGI::Session.

       For details, see: http://rt.cpan.org/Public/Bug/Display.html?id=28516 (and ...id=21981).

TRANSLATIONS
       This document is also available in Japanese.

       o   Translation based on 4.14: http://digit.que.ne.jp/work/index.cgi?Perldoc/ja

       o   Translation based on 3.11, including Cookbook and Tutorial:
	   http://perldoc.jp/docs/modules/CGI-Session-3.11/

TO LEARN MORE
       Current manual is optimized to be used as a quick reference. To learn more both about the
       philosophy and CGI::Session programming style, consider the following:

       o   CGI::Session::Tutorial - extended CGI::Session manual. Also includes library
	   architecture and driver specifications.

       o   We also provide mailing lists for CGI::Session users. To subscribe to the list or
	   browse the archives visit
	   https://lists.sourceforge.net/lists/listinfo/cgi-session-user

       o   RFC 2965 - "HTTP State Management Mechanism" found at
	   ftp://ftp.isi.edu/in-notes/rfc2965.txt

       o   CGI - standard CGI library

       o   Apache::Session - another fine alternative to CGI::Session.

METHODS
       Following is the overview of all the available methods accessible via CGI::Session object.

   new()
   new( $sid )
   new( $query )
   new( $dsn, $query||$sid )
   new( $dsn, $query||$sid, \%dsn_args )
   new( $dsn, $query||$sid, \%dsn_args, \%session_params )
       Constructor. Returns new session object, or undef on failure. Error message is accessible
       through errstr() - class method. If called on an already initialized session will re-
       initialize the session based on already configured object. This is only useful after a
       call to load().

       Can accept up to three arguments, $dsn - Data Source Name, $query||$sid - query object OR
       a string representing session id, and finally, \%dsn_args, arguments used by $dsn
       components.

       If called without any arguments, $dsn defaults to driver:file;serializer:default;id:md5,
       $query||$sid defaults to "CGI->new()", and "\%dsn_args" defaults to undef.

       If called with a single argument, it will be treated either as $query object, or $sid,
       depending on its type. If argument is a string , "new()" will treat it as session id and
       will attempt to retrieve the session from data store. If it fails, will create a new
       session id, which will be accessible through id() method. If argument is an object,
       cookie() and param() methods will be called on that object to recover a potential $sid and
       retrieve it from data store. If it fails, "new()" will create a new session id, which will
       be accessible through id() method. "name()" will define the name of the query parameter
       and/or cookie name to be requested, defaults to CGISESSID.

       If called with two arguments first will be treated as $dsn, and second will be treated as
       $query or $sid or undef, depending on its type. Some examples of this syntax are:

	   $s = CGI::Session->new("driver:mysql", undef);
	   $s = CGI::Session->new("driver:sqlite", $sid);
	   $s = CGI::Session->new("driver:db_file", $query);
	   $s = CGI::Session->new("serializer:storable;id:incr", $sid);
	   # etc...

       Briefly, "new()" will return an initialized session object with a valid id, whereas
       "load()" may return an empty session object with an undefined id.

       Tests are provided (t/new_with_undef.t and t/load_with_undef.t) to clarify the result of
       calling "new()" and "load()" with undef, or with an initialized CGI object with an
       undefined or fake CGISESSID.

       You are strongly advised to run the old-fashioned 'make test TEST_FILES=t/new_with_undef.t
       TEST_VERBOSE=1' or the new-fangled 'prove -v t/new_with_undef.t', for both new*.t and
       load*.t, and examine the output.

       Following data source components are supported:

       o   driver - CGI::Session driver. Available drivers are file, db_file, mysql and sqlite.
	   Third party drivers are welcome. For driver specs consider CGI::Session::Driver

       o   serializer - serializer to be used to encode the data structure before saving in the
	   disk. Available serializers are storable, freezethaw and default. Default serializer
	   will use Data::Dumper.

       o   id - ID generator to use when new session is to be created. Available ID generator is
	   md5

       For example, to get CGI::Session store its data using DB_File and serialize data using
       FreezeThaw:

	   $s = new CGI::Session("driver:DB_File;serializer:FreezeThaw", undef);

       If called with three arguments, first two will be treated as in the previous example, and
       third argument will be "\%dsn_args", which will be passed to $dsn components (namely,
       driver, serializer and id generators) for initialization purposes. Since all the $dsn
       components must initialize to some default value, this third argument should not be
       required for most drivers to operate properly.

       If called with four arguments, the first three match previous examples. The fourth
       argument must be a hash reference with parameters to be used by the CGI::Session object.
       (see \%session_params above )

       The following is a list of the current keys:

       o   name - Name to use for the cookie/query parameter name. This defaults to CGISESSID.
	   This can be altered or accessed by the "name" accessor.

       undef is acceptable as a valid placeholder to any of the above arguments, which will force
       default behavior.

   load()
   load( $query||$sid )
   load( $dsn, $query||$sid )
   load( $dsn, $query, \%dsn_args )
   load( $dsn, $query, \%dsn_args, \%session_params )
       Accepts the same arguments as new(), and also returns a new session object, or undef on
       failure.  The difference is, new() can create a new session if it detects expired and non-
       existing sessions, but "load()" does not.

       "load()" is useful to detect expired or non-existing sessions without forcing the library
       to create new sessions. So now you can do something like this:

	   $s = CGI::Session->load() or die CGI::Session->errstr();
	   if ( $s->is_expired ) {
	       print $s->header(),
		   $cgi->start_html(),
		   $cgi->p("Your session timed out! Refresh the screen to start new session!")
		   $cgi->end_html();
	       exit(0);
	   }

	   if ( $s->is_empty ) {
	       $s = $s->new() or die $s->errstr;
	   }

       Notice: All expired sessions are empty, but not all empty sessions are expired!

       Briefly, "new()" will return an initialized session object with a valid id, whereas
       "load()" may return an empty session object with an undefined id.

       Tests are provided (t/new_with_undef.t and t/load_with_undef.t) to clarify the result of
       calling "new()" and "load()" with undef, or with an initialized CGI object with an
       undefined or fake CGISESSID.

       You are strongly advised to run the old-fashioned 'make test TEST_FILES=t/new_with_undef.t
       TEST_VERBOSE=1' or the new-fangled 'prove -v t/new_with_undef.t', for both new*.t and
       load*.t, and examine the output.

   id()
       Returns effective ID for a session. Since effective ID and claimed ID can differ, valid
       session id should always be retrieved using this method.

   param($name)
   param(-name=>$name)
       Used in either of the above syntax returns a session parameter set to $name or undef if it
       doesn't exist. If it's called on a deleted method param() will issue a warning but return
       value is not defined.

   param($name, $value)
   param(-name=>$name, -value=>$value)
       Used in either of the above syntax assigns a new value to $name parameter, which can later
       be retrieved with previously introduced param() syntax. $value may be a scalar, arrayref
       or hashref.

       Attempts to set parameter names that start with _SESSION_ will trigger a warning and undef
       will be returned.

   param_hashref()
       Deprecated. Use dataref() instead.

   dataref()
       Returns reference to session's data table:

	   $params = $s->dataref();
	   $sid = $params->{_SESSION_ID};
	   $name= $params->{name};
	   # etc...

       Useful for having all session data in a hashref, but too risky to update.

   save_param()
   save_param($query)
   save_param($query, \@list)
       Saves query parameters to session object. In other words, it's the same as calling
       param($name, $value) for every single query parameter returned by "$query->param()". The
       first argument, if present, should be either CGI object or any object which can provide
       param() method. If it's undef, defaults to the return value of query(), which returns
       "CGI->new". If second argument is present and is a reference to an array, only those query
       parameters found in the array will be stored in the session. undef is a valid placeholder
       for any argument to force default behavior.

   load_param()
   load_param($query)
   load_param($query, \@list)
       Loads session parameters into a query object. The first argument, if present, should be
       query object, or any other object which can provide param() method. If second argument is
       present and is a reference to an array, only parameters found in that array will be loaded
       to the query object.

   clear()
   clear('field')
   clear(\@list)
       Clears parameters from the session object.

       With no parameters, all fields are cleared. If passed a single parameter or a reference to
       an array, only the named parameters are cleared.

   flush()
       Synchronizes data in memory  with the copy serialized by the driver. Call flush() if you
       need to access the session from outside the current session object. You should at least
       call flush() before your program exits.

       As a last resort, CGI::Session will automatically call flush for you just before the
       program terminates or session object goes out of scope. This automatic behavior was the
       recommended behavior until the 4.x series. Automatic flushing has since proven to be
       unreliable, and in some cases is now required in places that worked with 3.x. For further
       details see:

	http://rt.cpan.org/Ticket/Display.html?id=17541
	http://rt.cpan.org/Ticket/Display.html?id=17299

       Consequently, always explicitly calling "flush()" on the session before the program exits
       should be regarded as mandatory until this problem is rectified.

       Warning: A bug in your logic whereby the DBI handle has gone out out of scope before
       flush() is called means flush() won't work (when the session is a database session), so
       don't do that.

   atime()
       Read-only method. Returns the last access time of the session in seconds from epoch. This
       time is used internally while auto-expiring sessions and/or session parameters.

   ctime()
       Read-only method. Returns the time when the session was first created in seconds from
       epoch.

   expire()
   expire($time)
   expire($param, $time)
       Sets expiration interval relative to atime().

       If used with no arguments, returns the expiration interval if it was ever set. If no
       expiration was ever set, returns undef. For backwards compatibility, a method named
       "etime()" does the same thing.

       Second form sets an expiration time. This value is checked when previously stored session
       is asked to be retrieved, and if its expiration interval has passed, it will be expunged
       from the disk immediately. Passing 0 cancels expiration.

       By using the third syntax you can set the expiration interval for a particular session
       parameter, say ~logged-in. This would cause the library call clear() on the parameter when
       its time is up. Note it only makes sense to set this value to something earlier than when
       the whole session expires.  Passing 0 cancels expiration.

       All the time values should be given in the form of seconds. Following keywords are also
       supported for your convenience:

	   +-----------+---------------+
	   |   alias   |   meaning     |
	   +-----------+---------------+
	   |	 s     |   Second      |
	   |	 m     |   Minute      |
	   |	 h     |   Hour        |
	   |	 d     |   Day	       |
	   |	 w     |   Week        |
	   |	 M     |   Month       |
	   |	 y     |   Year        |
	   +-----------+---------------+

       Examples:

	   $session->expire("2h");		  # expires in two hours
	   $session->expire(0); 		  # cancel expiration
	   $session->expire("~logged-in", "10m"); # expires '~logged-in' parameter after 10 idle minutes

       Note: all the expiration times are relative to session's last access time, not to its
       creation time. To expire a session immediately, call delete(). To expire a specific
       session parameter immediately, call clear([$name]).

   is_new()
       Returns true only for a brand new session.

   is_expired()
       Tests whether session initialized using load() is to be expired. This method works only on
       sessions initialized with load():

	   $s = CGI::Session->load() or die CGI::Session->errstr;
	   if ( $s->is_expired ) {
	       die "Your session expired. Please refresh";
	   }
	   if ( $s->is_empty ) {
	       $s = $s->new() or die $s->errstr;
	   }

   is_empty()
       Returns true for sessions that are empty. It's preferred way of testing whether requested
       session was loaded successfully or not:

	   $s = CGI::Session->load($sid);
	   if ( $s->is_empty ) {
	       $s = $s->new();
	   }

       Actually, the above code is nothing but waste. The same effect could've been achieved by
       saying:

	   $s = CGI::Session->new( $sid );

       is_empty() is useful only if you wanted to catch requests for expired sessions, and create
       new session afterwards. See is_expired() for an example.

   delete()
       Deletes a session from the data store and empties session data from memory, completely, so
       subsequent read/write requests on the same object will fail. Technically speaking, though,
       it will only set the object's status to STATUS_DELETED.

       The intention is that in due course (of the program's execution) this will trigger
       flush(), and flush() will do the actual removal.

       However: Auto-flushing can be unreliable, and always explicitly calling "flush()" on the
       session after "delete()" should be regarded as mandatory until this problem is rectified.

       Warning: A bug in your logic whereby the DBI handle has gone out out of scope before
       flush() is called means flush() won't work (when the session is a database session), so
       don't do that.

   find( \&code )
   find( $dsn, \&code )
   find( $dsn, \&code, \%dsn_args )
       Experimental feature. Executes \&code for every session object stored in disk, passing
       initialized CGI::Session object as the first argument of \&code. Useful for housekeeping
       purposes, such as for removing expired sessions. Following line, for instance, will remove
       sessions already expired, but are still in disk:

       The following line, for instance, will remove sessions already expired, but which are
       still on disk:

	   CGI::Session->find( sub {} );

       Notice, above \&code didn't have to do anything, because load(), which is called to
       initialize sessions inside find(), will automatically remove expired sessions. Following
       example will remove all the objects that are 10+ days old:

	   CGI::Session->find( \&purge );
	   sub purge {
	       my ($session) = @_;
	       next if $session->is_empty;    # <-- already expired?!
	       if ( ($session->ctime + 3600*240) <= time() ) {
		   $session->delete() or warn "couldn't remove " . $session->id . ": " . $session->errstr;
	       }
	   }

       Note: find will not change the modification or access times on the sessions it returns.

       Explanation of the 3 parameters to "find()":

       $dsn
	   This is the DSN (Data Source Name) used by CGI::Session to control what type of
	   sessions you previously created and what type of sessions you now wish method "find()"
	   to pass to your callback.

	   The default value is defined above, in the docs for method "new()", and is
	   'driver:file;serializer:default;id:md5'.

	   Do not confuse this DSN with the DSN arguments mentioned just below, under \%dsn_args.

       \&code
	   This is the callback provided by you (i.e. the caller of method "find()") which is
	   called by CGI::Session once for each session found by method "find()" which matches
	   the given $dsn.

	   There is no default value for this coderef.

	   When your callback is actually called, the only parameter is a session. If you want to
	   call a subroutine you already have with more parameters, you can achieve this by
	   creating an anonymous subroutine that calls your subroutine with the parameters you
	   want. For example:

	       CGI::Session->find($dsn, sub { my_subroutine( @_, 'param 1', 'param 2' ) } );
	       CGI::Session->find($dsn, sub { $coderef->( @_, $extra_arg ) } );

	   Or if you wish, you can define a sub generator as such:

	       sub coderef_with_args {
		   my ( $coderef, @params ) = @_;
		   return sub { $coderef->( @_, @params ) };
	       }

	       CGI::Session->find($dsn, coderef_with_args( $coderef, 'param 1', 'param 2' ) );

       \%dsn_args
	   If your $dsn uses file-based storage, then this hashref might contain keys such as:

	       {
		   Directory => Value 1,
		   NoFlock   => Value 2,
		   UMask     => Value 3
	       }

	   If your $dsn uses db-based storage, then this hashref contains (up to) 3 keys, and
	   looks like:

	       {
		   DataSource => Value 1,
		   User       => Value 2,
		   Password   => Value 3
	       }

	   These 3 form the DSN, username and password used by DBI to control access to your
	   database server, and hence are only relevant when using db-based sessions.

	   The default value of this hashref is undef.

       Note: find() is meant to be convenient, not necessarily efficient. It's best suited in
       cron scripts.

MISCELLANEOUS METHODS
   remote_addr()
       Returns the remote address of the user who created the session for the first time. Returns
       undef if variable REMOTE_ADDR wasn't present in the environment when the session was
       created.

   errstr()
       Class method. Returns last error message from the library.

   dump()
       Returns a dump of the session object. Useful for debugging purposes only.

   header()
       Replacement for CGI.pm's header() method. Without this method, you usually need to create
       a CGI::Cookie object and send it as part of the HTTP header:

	   $cookie = CGI::Cookie->new(-name=>$session->name, -value=>$session->id);
	   print $cgi->header(-cookie=>$cookie);

       You can minimize the above into:

	   print $session->header();

       It will retrieve the name of the session cookie from "$session-"name()> which defaults to
       $CGI::Session::NAME. If you want to use a different name for your session cookie, do
       something like following before creating session object:

	   CGI::Session->name("MY_SID");
	   $session = new CGI::Session(undef, $cgi, \%attrs);

       Now, $session->header() uses "MY_SID" as a name for the session cookie.

   query()
       Returns query object associated with current session object. Default query object class is
       CGI.pm.

   DEPRECATED METHODS
       These methods exist solely for for compatibility with CGI::Session 3.x.

       close()

       Closes the session. Using flush() is recommended instead, since that's exactly what a call
       to close() does now.

DISTRIBUTION
       CGI::Session consists of several components such as drivers, serializers and id
       generators. This section lists what is available.

   DRIVERS
       Following drivers are included in the standard distribution:

       o   file - default driver for storing session data in plain files. Full name:
	   CGI::Session::Driver::file

       o   db_file - for storing session data in BerkelyDB. Requires: DB_File.	Full name:
	   CGI::Session::Driver::db_file

       o   mysql - for storing session data in MySQL tables. Requires DBI and DBD::mysql.  Full
	   name: CGI::Session::Driver::mysql

       o   sqlite - for storing session data in SQLite. Requires DBI and DBD::SQLite.  Full name:
	   CGI::Session::Driver::sqlite

   SERIALIZERS
       o   default - default data serializer. Uses standard Data::Dumper.  Full name:
	   CGI::Session::Serialize::default.

       o   storable - serializes data using Storable. Requires Storable.  Full name:
	   CGI::Session::Serialize::storable.

       o   freezethaw - serializes data using FreezeThaw. Requires FreezeThaw.	Full name:
	   CGI::Session::Serialize::freezethaw

       o   yaml - serializes data using YAML. Requires YAML or YAML::Syck.  Full name:
	   CGI::Session::Serialize::yaml

   ID GENERATORS
       Following ID generators are available:

       o   md5 - generates 32 character long hexadecimal string. Requires Digest::MD5.	Full
	   name: CGI::Session::ID::md5.

       o   incr - generates incremental session ids.

       o   static - generates static session ids. CGI::Session::ID::static

CREDITS
       CGI::Session evolved to what it is today with the help of following developers. The list
       doesn't follow any strict order, but somewhat chronological. Specifics can be found in
       Changes file

       Andy Lester
       Brian King <mrbbking@mac.com>
       Olivier Dragon <dragon@shadnet.shad.ca>
       Adam Jacob <adam@sysadminsith.org>
       Igor Plisco <igor@plisco.ru>
       Mark Stosberg
       Matt LeBlanc <mleblanc@cpan.org>
       Shawn Sorichetti

COPYRIGHT
       Copyright (C) 2001-2005 Sherzod Ruzmetov <sherzodr@cpan.org>. All rights reserved.  This
       library is free software. You can modify and or distribute it under the same terms as Perl
       itself.

PUBLIC CODE REPOSITORY
       You can see what the developers have been up to since the last release by checking out the
       code repository. You can browse the Subversion repository from here:

	http://svn.cromedome.net/repos/CGI-Session

       Or check it directly with "svn" from here:

	https://svn.cromedome.net/repos/CGI-Session

SUPPORT
       If you need help using CGI::Session consider the mailing list. You can ask the list by
       sending your questions to cgi-session-user@lists.sourceforge.net .

       You can subscribe to the mailing list at
       https://lists.sourceforge.net/lists/listinfo/cgi-session-user .

       Bug reports can be submitted at http://rt.cpan.org/NoAuth/ReportBug.html?Queue=CGI-Session

AUTHOR
       Sherzod Ruzmetov <sherzodr@cpan.org>, http://author.handalak.com/

       Mark Stosberg became a co-maintainer during the development of 4.0. "markstos@cpan.org".
       Ron Savage became a co-maintainer during the development of 4.30. "rsavage@cpan.org".

SEE ALSO
       o   CGI::Session::Tutorial - extended CGI::Session manual

       o   RFC 2965 - "HTTP State Management Mechanism" found at
	   ftp://ftp.isi.edu/in-notes/rfc2965.txt

       o   CGI - standard CGI library

       o   Apache::Session - another fine alternative to CGI::Session

perl v5.16.3				    2014-06-10				  CGI::Session(3)
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