Release Notes

1.3.11 Feb, 26 2005, Reini Urban, Joel Uckelman:

Lots of bugfixes, and some feature and performance enhancements. A new EDIT_TOOLBAR from mediawiki, more page permission enhancements, reduced memory usage for pagelists which need no page content, related improvement for Old Markup? crashes because of PCRE memory exhaustion.
New <!plugin-list !> syntax and PhpWiki:PageListLibrary args.
Because of SQL changes you'd need to ?action=upgrade to update for SQL.

fixes:

fixed Today link in all templates if USE_PATH_INFO = false
fixed Plugin Manager fatal error line 222
utf-8 pagenames fixed (typed foreign names from IE)
CGI: no PATH_INFO fix
fix some too loose PhpWiki:PagePermissions for signed, but not authenticated users (admin, owner, creator), and edit and view for Bogo and Password users
security fix for create ACL: action=edit is now checked for create
fixed syntax errors in signin.tmpl
fixed important WikiDB bug with DEBUG > 0: wrong assertion around line 172 (#954648)
fixed flatfile Archive Cleaner? assertion
Rss Feed Plugin stability fix for empty feeds or broken connections
fixed Sidebar theme CSS, added existing dates to jscalendar
fixed PhpWiki:ImageLinks, broken since 1.3.10 (Bug #956068)
fixed lib/pear/File_Passwd loading
fixed missing DEBUG warnings (Support #954260)
Translate Text?: verbatim needed a pagebreak
fixed duplicate session_id warning with adodb
fixed adodb DbPassUser login
fixed external DbPassUser login
fixed adodb action=upgrade
fixed FilePassUser locking problems and session handling
fixed a lot of LDAP auth and group issues
fixed LDAP options handling (by John Cole)
fixed possible security problems: allowing only posixly strict usernames, and an actual LDAP Injection problem, detected by Steve Christey, MITRE.
honor s=wildcard arguments for WikiAdmin plugins
fixed flatfile assertion (#963268) - check existing previous version
fixed all msg references from index.php to config/config.ini
fixed immediate LANG and THEME in-session updates if not stored in prefs
fixed USER_AUTH_POLICY=old, use only USER_AUTH_ORDER methods (besides HttpAuth) and removed LDAP, POP3, IMAP default configs.
Related Changes?: fixed days links
fix Rename: Change pagename in all linked pages
fixed PhpWiki:PageChangeNotification for not-current users
fixed Up Load Plugin? for filenames with space (Bug #969532)
fixed label support for Create Toc Plugin (Bug #969495)
fixed Apache2 crashing with old markup and the Create Toc Plugin. Still cannot edit though.
catch fatals and request->args changes on dumping
fixed unneeded User Preferences plugin login screen on dumphtml
catch SOAP fatal on Google Plugin? without GOOGLE_LICENSE_KEY
silently ignore jshide argument on MacIE for Add Comment Plugin? and Create Toc Plugin
Php Wiki is now allow_call_time_pass_reference = Off safe (php.ini) Some external libraries are not (Pear_DB odbc, adodb oracle)
fixed sql statements for pagedata where it is not needed, fixing the typical Page List? memory exhaustion on simple page lists. cached_html is handled complete seperate now.
fixed crash after login, by eliminating endless recursion in group isAdmin() checks
fixed and improved WikiDB pageid caching.
fixed some Wiki Group? errors for WIKIPAGE and DB
fixed JS_SEARCHREPLACE
fixed xmlrpc to be able to use the native xmlrpc extension.
fixed xmlrpc wiki.listLinks method: "name" => "page" param
fixed Wiki Admin Utils? behaviour on POST
fixed strict login on "Db" (by Mikhail Vladimirov)
more /tmp warnings on flatfile (by Joel Uckelman)

changes:

WikiAdminSetAcl functional
enabled PhpWiki:PagePermissions for all admin plugins (no admin required): Remove, Rename, Replace, SetAcl, Chown
new Error-style with collapsed output of repeated messages
whitespace trim pagenames to avoid abuse
no double login page header, better login msg.
improved FileFinder include_path logic (NormalizeLocalFileName, ...)
- init global File Finder? to add proper include paths at startup
adds PHPWIKI_DIR to the front if started from another dir, lib/pear to the end.
- fix slashify for Windows
check more config-default and predefined constants
AutoSplit pagenames at subpage seperators, esp for Sidebar theme
improve Pagelist layout by equal pagename width for limited lists
added CPAN, OsFaq2, Wiki Lens to interwiki.map
External Search Plugin useimage arg (RFE #952323)
Simplified some strings for easier translation
added hash and object support for SessionPassUser userid session variable
Auth Page=>DB PassUser upgrade: delete existing Page prefs, if Db prefs are saved.
renamed DB_Session.php to DbSession.php
vastly improved french locale support, which is now complete (by Pierrick Meignen). english, german and french are now completely translated. The others partially.
improved SetupWiki (virgin setup) loading all required action pages in english, if no foreign translation found (by Pierrick Meignen)
show Related Changes? only if minimum two links on the current page.
Page Dump?: View Source? link, better actionpage usage, MessageID TZ
brought WikiUser (old) uptodate
added owner and acl fields to dumps
import GOOGLE_LICENSE_KEY and FORTUNE_DIR from config.ini
renamed global $Theme to $WikiTheme (gforge nameclash)
aggressive WikiDB and cache memory optimization: don't cache %content and _cached_html if not needed.
Page Dump? added format=backup: dump all revisions.
force mysql to use auto_increment page.id for performance reasons. call ?action=upgrade
extended all plugins which take "pages" and "exclude" params to accept <!plugin-list !> pagelists
improved Sql Result?: templates and variable expansion. automatic paging not yet.
use latest Pear DB features, which will break on older PearDB libs. (escapeSimple). Use INCLUDE_PATH to override.
INCLUDE_PATH is now prepended, not appended. PHPWIKI_DIR is forced to be first.
rewrote Old Text Formatting Rules, AnciennesR%E8glesDeFormatage for proper importing (PCRE+memory related crashes on older php's)
added extra page.cached_html column. ?action=upgrade or Php Wiki Administration? "Convert cached_html" is needed to convert your old pagedata "_cached_html".
page deletion is now undoable and being seen in Recent Changes. Purge pages by new admin button.
zipdump and dumphtml contains now images, buttons and css
improved _Wiki Translation? performance with gettext extension
moved Db Session? methods to extra files as with Wiki User? files.

new:

new ENABLE_EDIT_TOOLBAR (from mediawiki), JS_SEARCHREPLACE, Add Category?, Add Plugin? buttons
new other config options:
- ENABLE_PAGEPERM to turn off ACL (no owner at the statusline if off)
- FORTUNE_DIR to enable random quotes for new pages
implemented WikiDB page creator and ownership
added action=pdf: only page formatter missing
new XmlParser, HtmlParser: new libs for HTML->wiki import and htmlarea3 support
new pagename utf8 detection logic (from mediawiki)
new action=chown|setacl|rename|dump action shortcuts pointing to the plugin
new Syntax Highlighter? plugin (based on work by alecthomas), needs highlight from http://www.andre-simon.de/
new Ploticus Plugin?. Full application/xhtml+xml support not yet (javascript document.write() not supported with ENABLE_XHTML_XML)
new List Pages? plugin (by Dan Frankowski)
new TeX2pngPlugin (by Pierrick Meignen)
added support for ?force_unlock=1 parameter for stale File_Passwd locks (should not be needed anymore, we lock only when we actually change the passwd)
added mysql-4.1 fix at action=upgrade, added CACHE_CONTROL NONE => NO_CACHE config.ini fix to action=upgrade
author, owner, creator support for Wiki Admin?* and All Pages plugins:
- All Pages Created By Me?, All Pages Last Edited By Me?, All Pages Owned By Me?
added action revert, with button from action=diff
added option regex to WikiAdminSearchReplace
added oracle PearDB backend (by Philippe Vanhaesendonck)
added new <!plugin-list Plugin Name? args!> syntax within plugin args
new plugin Include Pages?, esp. for <!plugin-list !>
added template variable expansion support to the Create Page Plugin?
added paging support for simple one-column pagelists
added new Page List? options: cols, azhead, comma, commasep, ordered and enabled the new args on most plugins.
added experimental Search Highlight? feature (not for HTML yet)
added OverWrite All? button to loadfile action on the first page.
added Load & OverWrite? button to Php Wiki Administration?
performance: use cached static config/config.php, if it's writable by the webserver. (experimental)
added ACCESS_LOG_SQL &1: read, &2 write. new accesslog sql table. for various log analysis: abuse prevention, recent referrers.
added more Page Change Notification? on other actions: rename, remove. changed subject on create. Collapse mult. emails to one.
added Wiki Plugin Cached? support for image maps, static cache in uploads/ and SVG
added case-sensitive and regex searching
added new PhpWiki:WikiFormRich plugin
added new Append Text Plugin? (by Pascal Giard)
added RSS2 link (format=rss2) in Recent Changes. (no cloud channel yet)
added Php Wiki Administration? WikiDB buttons: Purge all empty unreferenced pages?, Convert cached_html?
(nyi) new experimental Moderated Page feature. (i.e. delayed POST actions)
new edit "] old markup [Convert?" button to convert and save to new markup.
new Link Database plugin and actionpage for the http://touchgraph.sourceforge.net/ WikiBrowser
new hyperwiki applet in Sidebar. See http://hypergraph.sourceforge.net/
new xmlrpc methods: putPage, mailPasswordToUser
new xmlrpc test framework
Wiki Spam prevention: On GOOGLE_LINKS_NOFOLLOW add rel=nowfollow to all external links, unless the author was authenticated.
action=upgrade performs now a mysql LOCK TABLE privileges check and fix,
action=upgrade asks now for the admin's user and password if not defined
re-enabled and updated configurator.php, which is called automatically on first install (empty config.ini)
added lib/ASCIIMathPHP and Ascii Math? plugin
added Analyse Access Log Sql Plugin? (by Charles Corrigan)

1.2.8 (the old-stable branch) Jan, 30 2005, Reini Urban:

register_globals=off fix: fix and centralize broken register_globals=off logic.
update message catalog

1.2.7 (the old-stable branch) Jan, 6 2005, Reini Urban: Php Wiki 1.2.7 backport cvs release-1_2-branch enhancements never released with 1.2.3-1.2.6:

full xhtml conformity
split_pagename in title and header to help google
"INSTALL.Mac OS X" added from cvs
lib/zipfile.php: Content-Disposition: attachment
lib/config.php, lib/stdlib.php: support new USE_LINK_ICONS and AUTOSPLIT_WIKIWORDS, better i18n $!Wiki Name Regexp?
re-added images/* LINK_ICONS, pre-calculate DATA_PATH
locale/*: fix and update strings and templates esp. for german,
index.php: urlparser extended to omit &start_debug=1 and other args
added minor_edit checkbox
print more meta tags: robots, favicon, language and PHPWIKI_VERSION

1.2.6 (the old-stable branch) Dec, 19 2004, Reini Urban: flatfile fixes and enhancement:

fixed !Title Search and Backlinks for flatfile.
enable Most Popular (hitcount storage) for flatfile

1.2.7 (the old-stable version) Jan, 6 2005, Reini Urban: Php Wiki 1.2.7 backport cvs release-1_2-branch enhancements never released with 1.2.3-1.2.6:

full xhtml conformity
split_pagename in title and header to help google
"INSTALL.Mac OS X" added from cvs
lib/zipfile.php: Content-Disposition: attachment
lib/config.php, lib/stdlib.php: support new USE_LINK_ICONS and AUTOSPLIT_WIKIWORDS, better i18n $!Wiki Name Regexp?
re-added images/* LINK_ICONS, pre-calculate DATA_PATH
locale/*: fix and update strings and templates esp. for german,
index.php: urlparser extended to omit &start_debug=1 and other args
added minor_edit checkbox
print more meta tags: robots, favicon, language and PHPWIKI_VERSION

1.2.6 (the old-stable version) Dec, 19 2004, Reini Urban: flatfile fixes and enhancement:

fixed !Title Search and Backlinks for flatfile.
enable Most Popular (hitcount storage) for flatfile

1.2.5 (the old-stable branch) Nov, 28 2004, Reini Urban:

works with register_globals=off
adds user/password to pgsql,
fix zip and dumpserial on dba, dbm, msql and file,
and fixes a minor (un)lock issue, displaying the (un)locked page afterwards and not the Front Page?.

1.3.10 May, 13 2004, Reini Urban, Joby Walker:

In short: paging support, adodb rewrite, permission problem fixed.

fixes:

fixed severe permission problem: Default permissions not honored. Everybody was able to edit.
set User Preferences for bool and int fixed
POP3 auth
dba open problems improved, but not generally fixed
fixed dba session reading, but still broken
support wikiword links and image links in Rich Table? content, backlinks still not working.
fixed navbar links in theme smaller, and made them default
fixed loading of localized pagenames on action=upgrade
fixed interwiki.map loading on certain Pretty Wiki? setups
re-enabled php-4.0.6 support (broken since 1.3.8: superglobals, array_key_exists), 4.0.4-pl1 and 4.0.5 do work, but not stable enough.
fix running phpwiki in "http://server/" (empty DATA_PATH)
fix PhpWiki:PrettyWiki detection: starter script includes index.php, and include main.php by its own to override certain config values.
fix Wiki Admin Remove? arguments passed from Wiki Admin Select, Wiki Admin Remove? deleted too many args if passed from Wiki Admin Select
session transportation improved, no db objects stored
Page Group? support for links? and subpages
Http Client? fixes for older php's
Rss Feed for allow_url_fopen=false, IMAGE support, empty ITEM list
Theme buttons are now also searched in the default theme
numerous other minor bugfixes.

changes:

ADODB update from ancient mysql-only, to 4.21 with all supported databases. transaction support, with mysql locking-workarounds
pear not in our include_path anymore: either use your pear or our pear, by adding it to your include_path or not. use now 1:1 copies of pear libs.
Create Toc? parses now headers with links and formatting optionally, if TOC_FULL_SYNTAX is defined
Page Change Notification?: userids, not emails are printed
default theme navbar consistency: linkButtons instead of action buttons
_WikiTranslation what=buttons, noT=1, nolinks=1
SetupWiki (virgin setup) also loads all mandatory pages now and overwrites Release Notes
Page Change Notification? changed subject to "Wiki Name? Page change %s", update your filters accordingly
action=upgrade now linked in Php Wiki Administration?, db: fix page.id auto_increment and ADD session.sess_ip
some internal Inline Parser? optimization
DBAuthParam statement syntax change: variables now like '$userid'

new:

new ini-style config instead of old index.php, by Joby Walker
paging support for pagelists longer than limit
Popular Nearby? plugin: same as the classic most popular footer
formatted single-line plugins supported
Related Changes? plugin: only those which are links at the current page
new Google Link? pref: add "G?" lookup on unknown links
added chinese language support, by Yan-ren Tsai (druryl)
added missing MacOSX buttons, by Carsten Klapp.
new Crao theme from http://wiki.crao.net, by Arnaud Fontaine and Laurent Lunati
extended PhpWiki:InlineImages markup (size, border, ...)

1.3.9-p1 May,5 2004, Reini Urban:

Bugfix patch for the following 1.3.9 problems:

Default permissions not honored. Everybody was able to edit.
set User Preferences for bool and int fixed
dba open problems improved
session transportation improved, no db objects stored
php-4.0.6 support re-enabled (superglobals, array_key_exists)
Wiki Admin Remove? deleted too many if args passed from Wiki Admin Select
Page Group? support for links? and subpages
disabled default dba sessions, broken!
Http Client? fixes for older php's
Rss Feed for allow_url_fopen=false, IMAGE support, empty ITEM list

1.2.4 (the old-stable version) May, 4 2004, Reini Urban:

improves possible deadlocks in DBA,
fixes problems with DBA open failures.

1.2.3 (the old-stable version) Apr, 29 2004, Reini Urban:

added the most popular footer for dba
added remove for dba
fixed a warning on info page

1.3.9 Apr, 12 2004, Reini Urban:

Bugfix release for the following 1.3.8 problems:

syntax errors in lib/plugin/Up Load?.php
syntax errors in lib/plugin/Wiki Admin Remove?.php
syntax error in schemas/mysql.sql
several path issues (cannot findfile...), which were caused by a chdir for bindtextdomain in lib/config.php.

Failed opening required 'lib/stdlib.php', templates/html.tmpl: not found, and more
added self-registration for Db Pass User?
added Go To? plugin, Rate It? action page

1.3.8 Jan-Apr 2004, Reini Urban:

External plugable authentification, DB prefs and sessions, some more fixes, docs, themes and plugins.

new Wiki User New? class (started by Carsten Klapp),
new Preferences (optionally from DB, no cookies anymore)
improved DB_Session (added ADODB + dba support, Who Is Online? support)
enabled Wiki Group? (Joby Walker and Reini Urban)
new individual Page Permissions? (enabled, but not yet enforced)
new Wiki Admin Rename?, Wiki Admin Search Replace?, Wiki Admin Set Acl?
several other new plugins: Wiki Poll?, Who Is Online?, Create Toc? (experimental), Add Comment?, _Wiki Translation? and Translate Text?, No Cache?, Up Load? (by Nathan Gass?, qubit and Reini Urban), Include Site Map? (by cuthbertcat and Reini Urban), Rich Table? (by Sameer D. Sahasrabuddhe), Create Page and Rate It? (by Dan Frankowski), Rss Feed (by Arnaud Fontaine)
added Inter Wiki image button support
added Japanese language support (by Tadashi Jokagi)
added sqlite support (thanks to Matthew Palmer)
added theme and plugin-specific Page List? column types and theme-specific User Preferences
added Email Verification? and Page Change Notification? (experimental)
added new sess_ip column (DB_Session) for ip-based robot throttling
Pear DB update, minor performance improvement for PearDB
Page List?: enhanced sortby + limit support, sortable gridbuttons enforced, cleanup.
minor theme/default overhaul, new theme/smaller, new experimental theme/wikilens
new theme/Wordpress by Mike Pickering
updated theme/Sidebar: box methods, fast jscalendar and easier to customize
more Old Style Table arguments, Photo Album? local fs support
preliminary action=upgrade (To import new pgsrc pages only yet. not for DB)
preliminary SOAP support
added Pdf Output? libraries
experimental javascript Search&Replace edit buttons
experimental old-browser compatibility code.
fixed Wiki Admin Select, Wiki Admin Remove?
fixed and improved XHTML dumps (css, images, unlinked pages, \r\r\n issue)
fixed ADODB limit problem, fixed dba on Windows PHP 4.3.x
fixed Block Parser? problem with "0" as text
fixed Unfold Subpages? sortby
fixes for PHP5 compatibility started
fixed gettext, setlocale and update_locale problems

1.3.4 until 1.3.7, 2002-2003 Jeff, Carsten and Steve Wainstead:

several stable releases with better documentation (most plugins) and various bugfixes.
Edit Meta Data? (by Michael Van Dam?) for example. (forgot what else was new)
Jochen Kalmbach's new User File Management? and User Registration? didn't went upstream. (personal uploads, ...)

1.3.3 early 2002, Jeff strikes back, with the help of Carsten Klapp:

major feature enhancements:
Cache all output and use a clever page cache. Get rid of plugin-head.
new Page Type? class. Formatter and Search engine rewrite.
Validator
broke several older plugins: Inter Wiki Search, Wiki Admin Select. broke image buttons
Carsten Klapp's beloved MACOSX theme, button factory and CSS wizardry in general.
XHTML dumps, Wiki Blog as page type.
Plugin Manager and several more plugins.

1.3.2 early 2002, Reini Urban strikes:

Start of external authorisation in the config, but not in code.
Store Preferences in the users Personal Page? (Jeff)
Sessions in DB, pear DB update
concept of Subpages, Unfold Subpages?, Site Map, All Pages, All Users, ...
Page List? (Jeff and Reini)
Several new plugins: Redirect To, plugin-head architecture. Normalize template names. Wiki Admin Select architecture: Wiki Admin Remove?
Visual Wiki, Tex To Png?, text2png + several cached plugins (by Johannes Große)
Php Weather (?), Prev Next?, image buttons,
Include Page (Joe Edelman), Frame Include? (Reini), Transclude (Jeff)
Calendar (contributed by ?), Calendar List?, Wiki Blog, ...

.... a small hole here .... (three years no detailed HISTORY. see the outline above)

Jeffs Hacks.

New database API. See lib/WikiDB.php and lib/WikiDB/backend.php for the bulk of the documentation on this. The new database can save multiple archived versions of each page. A mechanism for purging archived revisions is now in place as well. See the $ExpireParams setting in index.php, and lib/ArchiveCleaner.php for details. At this point, the DBA, MySQL and Postgres backends are functional. The DBA backend could use some performance optimization. The whole API is still subject to some change as I figure out a clean way to provide for a variety of (not all forseen) methods of indexing and searching the wiki.
New Wiki Plugin architecture.
New template engine. This needs to be documented further, but, for now, see lib/Template.php. On second thought, don't (lib/Template.php desperately needs refactoring, still.) The basic advance is that PHP4's ob_*() functions can be used to capture output from code that is run through =eval(). This allows the templates to be PHP code...
Edit preview button on the edit page. Now you can see what your edits look like before committing them.
Reworked the style-sheets. I still need to clean this up some more. I would appreciate comments and bug reports on it. So far I've only tested the new style sheets with Netscape 4.77 and Mozilla 0.9.3 (both running under Linux.)
Expanded syntax for text search, Searches like "wiki or web -page" (or "(wiki or web) and not page") will now do more-or-less what they look like they'll do.
Security Issues: Php Wiki will now work with PHP's register_globals set to off.

Php Wiki 1.3.x development branch.

Pagenames in PATH_INFO.
File uploads: see Php Wiki Administration?.
User Preferences.
Ugly Magic Php Wiki URLs for administrative links.

Php Wiki 1.2 is a huge advance over version 1.0:

Database support for MySQL, Postgresql, mSQL, flat file and the new dba_ library in PHP4 is included.
Internationalization: support for different languages, down to the source level, is included. German, Spanish, Swedish and Dutch are currently shipped with Php Wiki. An architecture is in place to easily add more languages.
New linking schemes using square brackets in addition to the old style BumpyText.
Administration features include page locking, dumping the Wiki to a zip file, and deleting pages.
A Most Popular page showing the most frequently hit pages.
Full HTML compliance.
Links at the bottom of pages describing relationships like incoming links from other pages and their hits, outgoing and their hits, and the most popular nearby pages.
Color page diffs between the current and previous version.
An info page to view page metadata.
Far more customization capability for the admin.
A templating system to separate the page HTML from the PHP code.
New markup constructs for <B>, <I>, <DD>, and more.
Tabless markup to supercede the older markup (both still supported).

Php Wiki 1.1.9 includes Spanish language pages, a full implementation for Postgresql, numerous bug fixes and more. See the HISTORY file for more info: http://phpwiki.sourceforge.net/phpwiki/HISTORY

Php Wiki 1.1.6 is a major revision of Php Wiki. The ability to have themes (via an easy-to-edit template system) has been added; the schema for MySQL has been completely overhauled, breaking the page details into columns (for efficiency we agreed not to put references in a separate table, so it's not completely normalized. "Don't let the best be the enemy of the good.")

Postgresql support has been added and the markup language is evolving, now allowing

<h2>

<h3>

<h4>

tags and a new way to make text bold, and of course the new linking scheme?.

There is a new feature on all pages called more info that gives you a low level detailed view of a page, which is probably more useful for debugging than anything.

As we move towards a 1.2 release we will be adding logging, top ten most active pages and other new features with the new database schema (and yes, these features will make it into the DBM version too). I also want to add mSQL support and test it under Zend, the new PHP4.

Below are the release notes for version 1.03, the last release of the 1.0 Php Wiki series. --Steve Wainstead, swain@panix.com

Php Wiki was written because I am so interested in Wiki Wiki Webs, and I haven't used PHP since version 2.0. I wanted to see how it had advanced.

Version 1.0 is a near-perfect clone of the Portland Pattern Repository, http://c2.com/cgi-bin/wiki?WikiWikiWeb. In truth, I was using the Wiki script you can download from there as a model; that Wiki lacks a number of features the PPR has, like Edit Copy?. So in truth Php Wiki is a kind of hybrid of the PPR and the generic Wiki you can get from there (which is written in Perl).

The one caveat of Php Wiki is the allowance of HTML if the line is preceded by a bar (or pipe, which is how I usually say it). (That's a '|'). It was very simple to add, and the idea came from a posting somewhere on the PPR about how AT&T had an internal Wiki clone and used the same technique. The ability to embed HTML is disabled by default for security reasons.

Version 1.01 includes a patch that fixes a small error with rendering <hr> lines. Thanks to Gerry Barksdale.

See the HISTORY file for a rundown on the whole development process if that sort of thing really interests you :-)

--Steve Wainstead

Php Wiki Documentation

Dernière modification le mardi 15 mars 2005 11:19:21