CGI::Session(3pm)

1CGI::Session(3)       User Contributed Perl Documentation      CGI::Session(3)
2
3
4

NAME

6       CGI::Session - persistent session data in CGI applications
7

SYNOPSIS

9           # Object initialization:
10           use CGI::Session;
11           $session = CGI::Session->new();
12
13           $CGISESSID = $session->id();
14
15           # Send proper HTTP header with cookies:
16           print $session->header();
17
18           # Storing data in the session:
19           $session->param('f_name', 'Sherzod');
20           # or
21           $session->param(-name=>'l_name', -value=>'Ruzmetov');
22
23           # Flush the data from memory to the storage driver at least before your
24           # program finishes since auto-flushing can be unreliable.
25           $session->flush();
26
27           # Retrieving data:
28           my $f_name = $session->param('f_name');
29           # or
30           my $l_name = $session->param(-name=>'l_name');
31
32           # Clearing a certain session parameter:
33           $session->clear(["l_name", "f_name"]);
34
35           # Expire '_is_logged_in' flag after 10 idle minutes:
36           $session->expire('is_logged_in', '+10m')
37
38           # Expire the session itself after 1 idle hour:
39           $session->expire('+1h');
40
41           # Delete the session for good:
42           $session->delete();
43           $session->flush(); # Recommended practice says use flush() after delete().
44

DESCRIPTION

46       CGI::Session provides an easy, reliable and modular session management
47       system across HTTP requests.
48

METHODS

50       Following is the overview of all the available methods accessible via
51       CGI::Session object.
52
53   new()
54   new( $sid )
55   new( $query )
56   new( $dsn, $query||$sid )
57   new( $dsn, $query||$sid, \%dsn_args )
58   new( $dsn, $query||$sid, \%dsn_args, \%session_params )
59       Constructor. Returns new session object, or undef on failure. Error
60       message is accessible through errstr() - class method. If called on an
61       already initialized session will re-initialize the session based on
62       already configured object. This is only useful after a call to load().
63
64       Can accept up to three arguments, $dsn - Data Source Name, $query||$sid
65       - query object OR a string representing session id, and finally,
66       \%dsn_args, arguments used by $dsn components.
67
68       If called without any arguments, $dsn defaults to
69       driver:file;serializer:default;id:md5, $query||$sid defaults to
70       "CGI->new()", and "\%dsn_args" defaults to undef.
71
72       If called with a single argument, it will be treated either as $query
73       object, or $sid, depending on its type. If argument is a string , new()
74       will treat it as session id and will attempt to retrieve the session
75       from data store. If it fails, will create a new session id, which will
76       be accessible through id() method. If argument is an object, cookie()
77       and param() methods will be called on that object to recover a
78       potential $sid and retrieve it from data store. If it fails, new() will
79       create a new session id, which will be accessible through id() method.
80       name() will define the name of the query parameter and/or cookie name
81       to be requested, defaults to CGISESSID.
82
83       If called with two arguments first will be treated as $dsn, and second
84       will be treated as $query or $sid or undef, depending on its type. Some
85       examples of this syntax are:
86
87           $s = CGI::Session->new("driver:mysql", undef);
88           $s = CGI::Session->new("driver:sqlite", $sid);
89           $s = CGI::Session->new("driver:db_file", $query);
90           $s = CGI::Session->new("serializer:storable;id:incr", $sid);
91           # etc...
92
93       Briefly, new() will return an initialized session object with a valid
94       id, whereas load() may return an empty session object with an undefined
95       id.
96
97       Tests are provided (t/new_with_undef.t and t/load_with_undef.t) to
98       clarify the result of calling new() and load() with undef, or with an
99       initialized CGI object with an undefined or fake CGISESSID.
100
101       You are strongly advised to run the old-fashioned 'make test
102       TEST_FILES=t/new_with_undef.t TEST_VERBOSE=1' or the new-fangled 'prove
103       -v t/new_with_undef.t', for both new*.t and load*.t, and examine the
104       output.
105
106       Following data source components are supported:
107
108       •   driver - CGI::Session driver. Available drivers are file, db_file,
109           mysql and sqlite. Third party drivers are welcome. For driver specs
110           consider CGI::Session::Driver
111
112       •   serializer - serializer to be used to encode the data structure
113           before saving in the disk. Available serializers are storable,
114           freezethaw and default. Default serializer will use Data::Dumper.
115
116       •   id - ID generator to use when new session is to be created.
117           Available ID generator is md5
118
119       For example, to get CGI::Session store its data using DB_File and
120       serialize data using FreezeThaw:
121
122           $s = CGI::Session->new("driver:DB_File;serializer:FreezeThaw", undef);
123
124       If called with three arguments, first two will be treated as in the
125       previous example, and third argument will be "\%dsn_args", which will
126       be passed to $dsn components (namely, driver, serializer and id
127       generators) for initialization purposes. Since all the $dsn components
128       must initialize to some default value, this third argument should not
129       be required for most drivers to operate properly.
130
131       If called with four arguments, the first three match previous examples.
132       The fourth argument must be a hash reference with parameters to be used
133       by the CGI::Session object. (see \%session_params above )
134
135       The following is a list of the current keys:
136
137       •   name - Name to use for the cookie/query parameter name. This
138           defaults to CGISESSID. This can be altered or accessed by the
139           "name" accessor.
140
141       undef is acceptable as a valid placeholder to any of the above
142       arguments, which will force default behavior.
143
144   load()
145   load( $query||$sid )
146   load( $dsn, $query||$sid )
147   load( $dsn, $query, \%dsn_args )
148   load( $dsn, $query, \%dsn_args, \%session_params )
149       Accepts the same arguments as new(), and also returns a new session
150       object, or undef on failure.  The difference is, new() can create a new
151       session if it detects expired and non-existing sessions, but load()
152       does not.
153
154       load() is useful to detect expired or non-existing sessions without
155       forcing the library to create new sessions. So now you can do something
156       like this:
157
158           $s = CGI::Session->load() or die CGI::Session->errstr();
159           if ( $s->is_expired ) {
160               print $s->header(),
161                   $cgi->start_html(),
162                   $cgi->p("Your session timed out! Refresh the screen to start new session!")
163                   $cgi->end_html();
164               exit(0);
165           }
166
167           if ( $s->is_empty ) {
168               $s = $s->new() or die $s->errstr;
169           }
170
171       Notice: All expired sessions are empty, but not all empty sessions are
172       expired!
173
174       Briefly, new() will return an initialized session object with a valid
175       id, whereas load() may return an empty session object with an undefined
176       id.
177
178       Tests are provided (t/new_with_undef.t and t/load_with_undef.t) to
179       clarify the result of calling new() and load() with undef, or with an
180       initialized CGI object with an undefined or fake CGISESSID.
181
182       You are strongly advised to run the old-fashioned 'make test
183       TEST_FILES=t/new_with_undef.t TEST_VERBOSE=1' or the new-fangled 'prove
184       -v t/new_with_undef.t', for both new*.t and load*.t, and examine the
185       output.
186
187   id()
188       Returns effective ID for a session. Since effective ID and claimed ID
189       can differ, valid session id should always be retrieved using this
190       method.
191
192   param($name)
193   param(-name=>$name)
194       Used in either of the above syntax returns a session parameter set to
195       $name or undef if it doesn't exist. If it's called on a deleted method
196       param() will issue a warning but return value is not defined.
197
198   param($name, $value)
199   param(-name=>$name, -value=>$value)
200       Used in either of the above syntax assigns a new value to $name
201       parameter, which can later be retrieved with previously introduced
202       param() syntax. $value may be a scalar, arrayref or hashref.
203
204       Attempts to set parameter names that start with _SESSION_ will trigger
205       a warning and undef will be returned.
206
207   param_hashref()
208       Deprecated. Use dataref() instead.
209
210   dataref()
211       Returns reference to session's data table:
212
213           $params = $s->dataref();
214           $sid = $params->{_SESSION_ID};
215           $name= $params->{name};
216           # etc...
217
218       Useful for having all session data in a hashref, but too risky to
219       update.
220
221   save_param()
222   save_param($query)
223   save_param($query, \@list)
224       Saves query parameters to session object. In other words, it's the same
225       as calling param($name, $value) for every single query parameter
226       returned by "$query->param()". The first argument, if present, should
227       be either CGI object or any object which can provide param() method. If
228       it's undef, defaults to the return value of query(), which returns
229       "CGI->new". If second argument is present and is a reference to an
230       array, only those query parameters found in the array will be stored in
231       the session. undef is a valid placeholder for any argument to force
232       default behavior.
233
234   load_param()
235   load_param($query)
236   load_param($query, \@list)
237       Loads session parameters into a query object. The first argument, if
238       present, should be query object, or any other object which can provide
239       param() method. If second argument is present and is a reference to an
240       array, only parameters found in that array will be loaded to the query
241       object.
242
243   clear()
244   clear('field')
245   clear(\@list)
246       Clears parameters from the session object.
247
248       With no parameters, all fields are cleared. If passed a single
249       parameter or a reference to an array, only the named parameters are
250       cleared.
251
252   flush()
253       Synchronizes data in memory with the copy serialized by the driver.
254       Call flush() if you need to access the session from outside the current
255       session object. You should call flush() sometime before your program
256       exits.
257
258       As a last resort, CGI::Session will automatically call flush for you
259       just before the program terminates or session object goes out of scope.
260       Automatic flushing has proven to be unreliable, and in some cases is
261       now required in places that worked with CGI::Session 3.x.
262
263       Always explicitly calling flush() on the session before the program
264       exits is recommended. For extra safety, call it immediately after every
265       important session update.
266
267       Also see "A Warning about Auto-flushing"
268
269   atime()
270       Read-only method. Returns the last access time of the session in
271       seconds from epoch. This time is used internally while auto-expiring
272       sessions and/or session parameters.
273
274   ctime()
275       Read-only method. Returns the time when the session was first created
276       in seconds from epoch.
277
278   expire()
279   expire($time)
280   expire($param, $time)
281       Sets expiration interval relative to atime().
282
283       If used with no arguments, returns the expiration interval if it was
284       ever set. If no expiration was ever set, returns undef. For backwards
285       compatibility, a method named etime() does the same thing.
286
287       Second form sets an expiration time. This value is checked when
288       previously stored session is asked to be retrieved, and if its
289       expiration interval has passed, it will be expunged from the disk
290       immediately. Passing 0 cancels expiration.
291
292       By using the third syntax you can set the expiration interval for a
293       particular session parameter, say ~logged-in. This would cause the
294       library call clear() on the parameter when its time is up. Note it only
295       makes sense to set this value to something earlier than when the whole
296       session expires.  Passing 0 cancels expiration.
297
298       All the time values should be given in the form of seconds. Following
299       keywords are also supported for your convenience:
300
301           +-----------+---------------+
302           |   alias   |   meaning     |
303           +-----------+---------------+
304           |     s     |   Second      |
305           |     m     |   Minute      |
306           |     h     |   Hour        |
307           |     d     |   Day         |
308           |     w     |   Week        |
309           |     M     |   Month       |
310           |     y     |   Year        |
311           +-----------+---------------+
312
313       Examples:
314
315           $session->expire("2h");                # expires in two hours
316           $session->expire(0);                   # cancel expiration
317           $session->expire("~logged-in", "10m"); # expires '~logged-in' parameter after 10 idle minutes
318
319       Note: all the expiration times are relative to session's last access
320       time, not to its creation time. To expire a session immediately, call
321       delete(). To expire a specific session parameter immediately, call
322       clear([$name]).
323
324   is_new()
325       Returns true only for a brand new session.
326
327   is_expired()
328       Tests whether session initialized using load() is to be expired. This
329       method works only on sessions initialized with load():
330
331           $s = CGI::Session->load() or die CGI::Session->errstr;
332           if ( $s->is_expired ) {
333               die "Your session expired. Please refresh";
334           }
335           if ( $s->is_empty ) {
336               $s = $s->new() or die $s->errstr;
337           }
338
339   is_empty()
340       Returns true for sessions that are empty. It's preferred way of testing
341       whether requested session was loaded successfully or not:
342
343           $s = CGI::Session->load($sid);
344           if ( $s->is_empty ) {
345               $s = $s->new();
346           }
347
348       Actually, the above code is nothing but waste. The same effect could've
349       been achieved by saying:
350
351           $s = CGI::Session->new( $sid );
352
353       is_empty() is useful only if you wanted to catch requests for expired
354       sessions, and create new session afterwards. See is_expired() for an
355       example.
356
357   ip_match()
358       Returns true if $ENV{REMOTE_ADDR} matches the remote address stored in
359       the session.
360
361       If you have an application where you are sure your users' IPs are
362       constant during a session, you can consider enabling an option to make
363       this check:
364
365           use CGI::Session '-ip_match';
366
367       Usually you don't call ip_match() directly, but by using the above
368       method. It is useful only if you want to call it inside of coderef
369       passed to the find() method.
370
371   delete()
372       Sets the objects status to be "deleted".  Subsequent read/write
373       requests on the same object will fail.  To physically delete it from
374       the data store you need to call flush().  CGI::Session attempts to do
375       this automatically when the object is being destroyed (usually as the
376       script exits), but see "A Warning about Auto-flushing".
377
378   find( \&code )
379   find( $dsn, \&code )
380   find( $dsn, \&code, \%dsn_args )
381       Experimental feature. Executes \&code for every session object stored
382       in disk, passing initialized CGI::Session object as the first argument
383       of \&code. Useful for housekeeping purposes, such as for removing
384       expired sessions. Following line, for instance, will remove sessions
385       already expired, but are still in disk:
386
387       The following line, for instance, will remove sessions already expired,
388       but which are still on disk:
389
390           CGI::Session->find( sub {} );
391
392       Notice, above \&code didn't have to do anything, because load(), which
393       is called to initialize sessions inside find(), will automatically
394       remove expired sessions. Following example will remove all the objects
395       that are 10+ days old:
396
397           CGI::Session->find( \&purge );
398           sub purge {
399               my ($session) = @_;
400               next if $session->is_empty;    # <-- already expired?!
401               if ( ($session->ctime + 3600*240) <= time() ) {
402                   $session->delete();
403                   $session->flush(); # Recommended practice says use flush() after delete().
404               }
405           }
406
407       Note: find will not change the modification or access times on the
408       sessions it returns.
409
410       Explanation of the 3 parameters to find():
411
412       $dsn
413           This is the DSN (Data Source Name) used by CGI::Session to control
414           what type of sessions you previously created and what type of
415           sessions you now wish method find() to pass to your callback.
416
417           The default value is defined above, in the docs for method new(),
418           and is 'driver:file;serializer:default;id:md5'.
419
420           Do not confuse this DSN with the DSN arguments mentioned just
421           below, under \%dsn_args.
422
423       \&code
424           This is the callback provided by you (i.e. the caller of method
425           find()) which is called by CGI::Session once for each session found
426           by method find() which matches the given $dsn.
427
428           There is no default value for this coderef.
429
430           When your callback is actually called, the only parameter is a
431           session. If you want to call a subroutine you already have with
432           more parameters, you can achieve this by creating an anonymous
433           subroutine that calls your subroutine with the parameters you want.
434           For example:
435
436               CGI::Session->find($dsn, sub { my_subroutine( @_, 'param 1', 'param 2' ) } );
437               CGI::Session->find($dsn, sub { $coderef->( @_, $extra_arg ) } );
438
439           Or if you wish, you can define a sub generator as such:
440
441               sub coderef_with_args {
442                   my ( $coderef, @params ) = @_;
443                   return sub { $coderef->( @_, @params ) };
444               }
445
446               CGI::Session->find($dsn, coderef_with_args( $coderef, 'param 1', 'param 2' ) );
447
448       \%dsn_args
449           If your $dsn uses file-based storage, then this hashref might
450           contain keys such as:
451
452               {
453                   Directory => Value 1,
454                   NoFlock   => Value 2,
455                   UMask     => Value 3
456               }
457
458           If your $dsn uses db-based storage, then this hashref contains (up
459           to) 3 keys, and looks like:
460
461               {
462                   DataSource => Value 1,
463                   User       => Value 2,
464                   Password   => Value 3
465               }
466
467           These 3 form the DSN, username and password used by DBI to control
468           access to your database server, and hence are only relevant when
469           using db-based sessions.
470
471           The default value of this hashref is undef.
472
473       Note: find() is meant to be convenient, not necessarily efficient. It's
474       best suited in cron scripts.
475
476   name($new_name)
477       The $new_name parameter is optional. If supplied it sets the query or
478       cookie parameter name to be used.
479
480       It defaults to $CGI::Session::NAME, which defaults to CGISESSID.
481
482       You are strongly discouraged from using the global variable
483       $CGI::Session::NAME, since it is deprecated (as are all global
484       variables) and will be removed in a future version of this module.
485
486       Return value: The current query or cookie parameter name.
487

MISCELLANEOUS METHODS

489   remote_addr()
490       Returns the remote address of the user who created the session for the
491       first time. Returns undef if variable REMOTE_ADDR wasn't present in the
492       environment when the session was created.
493
494   errstr()
495       Class method. Returns last error message from the library.
496
497   dump()
498       Returns a dump of the session object. Useful for debugging purposes
499       only.
500
501   header()
502       A wrapper for "CGI"'s header() method. Calling this method is
503       equivalent to something like this:
504
505           $cookie = CGI::Cookie->new(-name=>$session->name, -value=>$session->id);
506           print $cgi->header(-cookie=>$cookie, @_);
507
508       You can minimize the above into:
509
510           print $session->header();
511
512       It will retrieve the name of the session cookie from "$session-"name()>
513       which defaults to $CGI::Session::NAME. If you want to use a different
514       name for your session cookie, do something like this before creating
515       session object:
516
517           CGI::Session->name("MY_SID");
518           $session = CGI::Session->new(undef, $cgi, \%attrs);
519
520       Now, $session->header() uses "MY_SID" as the name for the session
521       cookie. For all additional options that can be passed, see the header()
522       docs in "CGI".
523
524   query()
525       Returns query object associated with current session object. Default
526       query object class is "CGI".
527
528   DEPRECATED METHODS
529       These methods exist solely for for compatibility with CGI::Session 3.x.
530
531       close()
532
533       Closes the session. Using flush() is recommended instead, since that's
534       exactly what a call to close() does now.
535

DISTRIBUTION

537       CGI::Session consists of several components such as drivers,
538       serializers and id generators. This section lists what is available.
539
540   DRIVERS
541       The following drivers are included in the standard distribution:
542
543       •   file - default driver for storing session data in plain files. Full
544           name: CGI::Session::Driver::file
545
546       •   db_file - for storing session data in BerkelyDB. Requires: DB_File.
547           Full name: CGI::Session::Driver::db_file
548
549       •   mysql - for storing session data in MySQL tables. Requires DBI and
550           DBD::mysql.  Full name: CGI::Session::Driver::mysql
551
552       •   sqlite - for storing session data in SQLite. Requires DBI and
553           DBD::SQLite.  Full name: CGI::Session::Driver::sqlite
554
555       Other drivers are available from CPAN.
556
557   SERIALIZERS
558       •   default - default data serializer. Uses standard Data::Dumper.
559           Full name: CGI::Session::Serialize::default.
560
561       •   storable - serializes data using Storable. Requires Storable.  Full
562           name: CGI::Session::Serialize::storable.
563
564       •   freezethaw - serializes data using FreezeThaw. Requires FreezeThaw.
565           Full name: CGI::Session::Serialize::freezethaw
566
567       •   yaml - serializes data using YAML. Requires YAML or YAML::Syck.
568           Full name: CGI::Session::Serialize::yaml
569
570   ID GENERATORS
571       The following ID generators are included in the standard distribution.
572
573       •   md5 - generates 32 character long hexadecimal string. Requires
574           Digest::MD5.  Full name: CGI::Session::ID::md5.
575
576       •   incr - generates incremental session ids.
577
578       •   static - generates static session ids. CGI::Session::ID::static
579

A Warning about Auto-flushing

581       Auto-flushing can be unreliable for the following reasons. Explicit
582       flushing after key session updates is recommended.
583
584       If the "DBI" handle goes out of scope before the session variable
585           For database-stored sessions, if the "DBI" handle has gone out of
586           scope before the auto-flushing happens, auto-flushing will fail.
587
588       Circular references
589           If the calling code contains a circular reference, it's possible
590           that your "CGI::Session" object will not be destroyed until it is
591           too late for auto-flushing to work. You can find circular
592           references with a tool like Devel::Cycle.
593
594           In particular, these modules are known to contain circular
595           references which lead to this problem:
596
597           CGI::Application::Plugin::DebugScreen V 0.06
598           CGI::Application::Plugin::ErrorPage before version 1.20
599       Signal handlers
600           If your application may receive signals, there is an increased
601           chance that the signal will arrive after the session was updated
602           but before it is auto-flushed at object destruction time.
603

A Warning about UTF8

605       You are strongly encouraged to refer to, at least, the first of these
606       articles, for help with UTF8.
607
608       <http://en.wikibooks.org/wiki/Perl_Programming/Unicode_UTF-8>
609
610       <http://perl.bristolbath.org/blog/lyle/2008/12/giving-cgiapplication-internationalization-i18n.html>
611
612       <http://metsankulma.homelinux.net/cgi-bin/l10n_example_4/main.cgi>
613
614       <http://rassie.org/archives/247>
615
616       <http://www.di-mgt.com.au/cryptoInternational2.html>
617
618       Briefly, these are the issues:
619
620       The file containing the source code of your program
621           Consider "use utf8;" or "use encoding 'utf8';".
622
623       Influencing the encoding of the program's input
624           Use:
625
626               binmode STDIN, ":encoding(utf8)";.
627
628               Of course, the program can get input from other sources, e.g. HTML template files, not just STDIN.
629
630       Influencing the encoding of the program's output
631           Use:
632
633               binmode STDOUT, ":encoding(utf8)";
634
635               When using CGI.pm, you can use $q->charset('UTF-8'). This is the same as passing 'UTF-8' to CGI's C<header()> method.
636
637               Alternately, when using CGI::Session, you can use $session->header(charset => 'utf-8'), which will be
638               passed to the query object's C<header()> method. Clearly this is preferable when the query object might not be
639               of type CGI.
640
641               See L</header()> for a fuller discussion of the use of the C<header()> method in conjunction with cookies.
642

TRANSLATIONS

644       This document is also available in Japanese.
645
646       o   Translation based on 4.14:
647           http://digit.que.ne.jp/work/index.cgi?Perldoc/ja
648
649       o   Translation based on 3.11, including Cookbook and Tutorial:
650           http://perldoc.jp/docs/modules/CGI-Session-3.11/
651

CREDITS

653       CGI::Session evolved to what it is today with the help of following
654       developers. The list doesn't follow any strict order, but somewhat
655       chronological. Specifics can be found in Changes file
656
657       Andy Lester
658       Brian King <mrbbking@mac.com>
659       Olivier Dragon <dragon@shadnet.shad.ca>
660       Adam Jacob <adam@sysadminsith.org>
661       Igor Plisco <igor@plisco.ru>
662       Mark Stosberg
663       Matt LeBlanc <mleblanc@cpan.org>
664       Shawn Sorichetti
665       Ron Savage
666       Rhesa Rozendaal
667           He suggested Devel::Cycle to help debugging.
668
669       Also, many people on the CGI::Application and CGI::Session mailing
670       lists have contributed ideas and suggestions, and battled publicly with
671       bugs, all of which has helped.
672

COPYRIGHT

674       Copyright (C) 2001-2005 Sherzod Ruzmetov <sherzodr@cpan.org>. All
675       rights reserved.  This library is free software. You can modify and or
676       distribute it under the same terms as Perl itself.
677

PUBLIC CODE REPOSITORY

679       You can see what the developers have been up to since the last release
680       by checking out the code repository. You can browse the git repository
681       from here:
682
683        http://github.com/cromedome/cgi-session/tree/master
684
685       Or check out the code with:
686
687        git clone git://github.com/cromedome/cgi-session.git
688

SUPPORT

690       If you need help using CGI::Session, ask on the mailing list. You can
691       ask the list by sending your questions to
692       cgi-session-user@lists.sourceforge.net .
693
694       You can subscribe to the mailing list at
695       https://lists.sourceforge.net/lists/listinfo/cgi-session-user .
696
697       Bug reports can be submitted at
698       http://rt.cpan.org/NoAuth/ReportBug.html?Queue=CGI-Session
699

AUTHOR

701       Sherzod Ruzmetov "sherzodr@cpan.org"
702
703       Mark Stosberg became a co-maintainer during the development of 4.0.
704       "markstos@cpan.org".
705
706       Ron Savage became a co-maintainer during the development of 4.30.
707       "rsavage@cpan.org".
708
709       If you would like support, ask on the mailing list as describe above.
710       The maintainers and other users are subscribed to it.
711