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{{TNT|ExtensionTypes}}
[[File:MediaWiki-extensions-icon.svg|125px|alt=MediaWiki extensions|right]]
{{mbox| text = If you intend to have your extension deployed on Wikimedia sites, read {{ll|Writing an extension for deployment}}}}
Each [[Special:MyLanguage/Manual:Extensions|extension]] consists of three parts:
# [[#Setup|Setup]]
# [[#Execution|Execution]]
# [[#Localisation|Localisation]]
A minimal extension will consist of three files, one for each part:
; ''MyExtension''/extension.json: Stores the [[#Setup|setup]] instructions. The file name must be ''extension.json''. (Prior to MediaWiki 1.25 the setup instructions were in a <tt>''MyExtension''/''MyExtension''.php</tt> file named after the extension. Many extensions still have backwards-compatibility shims in this PHP file.)
; ''MyExtension''/''MyExtension''_body.php: Stores the [[#Execution|execution]] code for the extension. The file name ''MyExtension_body.php'' is conventional but not required. If your extension is complex and involves multiple PHP files, you should follow the convention to put its implementation code in a subdirectory named <tt>''MyExtension''/includes</tt> (although the Example and BoilerPlate extensions do not follow this convention). For example, see the {{git file | project=mediawiki/extensions/SemanticMediaWiki | file=includes |text=Semantic MediaWiki}} extension.
; ''MyExtension''/i18n/*.json: Stores [[#Localisation|localisation]] information for the extension.
{{TNT|Note}} Originally, extensions were single files, and you may still find some examples of this deprecated style.
When you develop an extension, replace ''MyExtension'' above with the name of your extension.
Use ''UpperCamelCase'' names for its directory and PHP file(s); this is the general [[Special:MyLanguage/Manual:Coding_conventions#File naming|file naming]] convention.<ref>[[mailarchive:wikitech-l/2011-August/054839.html]]</ref>
(The {{git repo|project=mediawiki/extensions/BoilerPlate | text=Boilerplate extension}} is a good starting point for your extension. Also check out the [https://github.com/JonasGroeger/cookiecutter-mediawiki-extension cookiecutter template for MediaWiki extensions on GitHub].)
The three parts of an extension, [[#Setup|setup]], [[#Execution|execution]], and, [[#Localisation|localisation]] as well as [[#Extension types|extension types]] and [[#Licensing|licensing]] and [[#Publishing|publishing your extension]] are described in the following sections of this page.
{{TNT|Note}} While developing, you may want to disable caching by setting {{ll|Manual:$wgMainCacheType|$wgMainCacheType}} = CACHE_NONE and {{ll|Manual:$wgCacheDirectory|$wgCacheDirectory}} = false, otherwise system messages and other changes may not show up.
{{anchor|Setup}}
== Setup ==
{{ombox| text = MediaWiki 1.25 introduces a [[Special:MyLanguage/extension registration|new way]] to load an extension. For details on how to write an extension for older versions of MediaWiki, see an [//www.mediawiki.org/w/index.php?title=Manual:Developing_extensions&oldid=1655961 older revision].}}
Your goal in writing the setup portion is to consolidate set up so that users installing your extension need do nothing more than include the setup file in their {{ll|Manual:LocalSettings.php|LocalSettings.php}} file, like this:
<syntaxhighlight lang="php">
wfLoadExtension( 'MyExtension' );
</syntaxhighlight>
If you want to make your extension user configurable, you need to define and document some configuration parameters and your users' setup should look something like this:
<syntaxhighlight lang="php">
wfLoadExtension( 'MyExtension' );
$wgMyExtensionConfigThis = 1;
$wgMyExtensionConfigThat = false;
</syntaxhighlight>
To reach this simplicity, your setup file needs to accomplish a number of tasks (described in detail in the following sections):
* register any [[Special:MyLanguage/Manual:Media handler|media handler]], [[Special:MyLanguage/Manual:Parser functions|parser function]], [[Special:MyLanguage/Manual:Special pages|special page]], [[Special:MyLanguage/Manual:Tag extensions|custom XML tag]], and [[Special:MyLanguage/Manual:Variable|variable]] used by your extension.
* define and/or validate any configuration variables you have defined for your extension.
* prepare the classes used by your extension for autoloading
* determine what parts of your setup should be done immediately and what needs to be deferred until the MediaWiki core has been initialized and configured
* define any additional [[Special:MyLanguage/Manual:Hooks|hooks]] needed by your extension
* create or check any new database tables required by your extension.
* set up localisation for your extension
===Registering features with MediaWiki===
MediaWiki lists all the extensions that have been installed on its <code><nowiki>Special:Version</nowiki></code> page. For example, you can see all the extensions installed on this wiki at [[Special:Version]]. It is good form to make sure that your extension is also listed on this page. To do this, you will need to add an entry to {{ll|Manual:$wgExtensionCredits|$wgExtensionCredits}} for '''each''' [[Special:MyLanguage/Manual:Media handler|media handler]], [[Special:MyLanguage/Manual:Parser functions|parser function]], [[Special:MyLanguage/Manual:Special pages|special page]], [[Special:MyLanguage/Manual:Tag extensions|custom XML tag]], and [[Special:MyLanguage/Manual:Variable|variable]] used by your extension. The entry will look something like this:
<syntaxhighlight lang="json">
{
"name": "Example",
"author": "John Doe",
"url": "https://www.mediawiki.org/wiki/Extension:Example",
"description": "This extension is an example and performs no discernible function",
"version": "1.5",
"license-name": "",
"type": "validextensionclass",
"manifest_version": 1
}
</syntaxhighlight>
See {{ll|Manual:$wgExtensionCredits}} for full details on what these fields do.
Many of the fields are optional, but it's still good practice to fill them out. The <code>manifest_version</code> refers to the version of the schema the {{ll|extension.json|extension.json}} file is written against. As of writing (1.26alpha), the only supported version is 1.
In addition to the above registration, you must also "hook" your feature into MediaWiki. The above only sets up the Special:Version page. The way you do this depends on [[#Extension types|the type of your extension]]. For details, please see the documentation for each type of extension:
{{TNT|ExtensionTypes}}
===Making your extension user configurable===
If you want your user to be able to configure your extension, you'll need to provide one or more configuration variables. It is a good idea to give those variables a unique name. They should also follow MediaWiki [[Special:MyLanguage/Manual:Coding_conventions/PHP#Naming|naming conventions]] (e.g. global variables should begin with $wg).
For example, if your extension is named "Very silly extension that does nothing", you might want to name all your configuration variables to begin <code>$wgVsetdn</code> or <code>$wgVSETDN</code>. It doesn't really matter what you choose so long as <em>none</em> of the MediaWiki core begins its variables this way and you have done a reasonable job of checking to see that none of the published extensions begin their variables this way. Users won't take kindly to having to choose between your extension and some other extensions because you chose overlapping variable names.
It is also a good idea to include extensive documentation of any configuration variables in your installation notes.
{{ {{TNTN|Warning}} |1=To avoid <tt>[[Special:MyLanguage/Register globals|register_globals]]</tt> vulnerabilities, '''ALWAYS''' explicitly set all your extension's configuration variables in extension setup file. Constructs like <tt>if ( !isset( $wgMyLeetOption ) ) $wgMyLeetOption = somevalue;</tt> '''do not''' safeguard against register_globals!}}
Here is an example boiler plate that can be used to get started:
<syntaxhighlight lang="json">
{
"name": "BoilerPlate",
"version": "0.0.0",
"author": [
"Your Name"
],
"url": "https://www.mediawiki.org/wiki/Extension:BoilerPlate",
"descriptionmsg": "boilerplate-desc",
"license-name": "MIT",
"type": "other",
"AutoloadClasses": {
"BoilerPlateHooks": "BoilerPlate.hooks.php",
"SpecialHelloWorld": "specials/SpecialHelloWorld.php"
},
"config": {
"BoilerPlateEnableFoo": true
},
"callback": "BoilerPlateHooks::onExtensionLoad",
"ExtensionMessagesFiles": {
"BoilerPlateAlias": "BoilerPlate.i18n.alias.php"
},
"Hooks": {
"NameOfHook": [
"BoilerPlateHooks::onNameOfHook"
]
},
"MessagesDirs": {
"BoilerPlate": [
"i18n"
]
},
"ResourceModules": {
"ext.boilerPlate.foo": {
"scripts": [
"modules/ext.boilerPlate.js",
"modules/ext.boilerPlate.foo.js"
],
"styles": [
"modules/ext.boilerPlate.foo.css"
]
}
},
"ResourceFileModulePaths": {
"localBasePath": "",
"remoteExtPath": "BoilerPlate"
},
"SpecialPages": {
"HelloWorld": "SpecialHelloWorld"
},
"manifest_version": 1
}
</syntaxhighlight>
===Preparing classes for autoloading===
If you choose to use classes to implement your extension, MediaWiki provides a simplified mechanism for helping PHP find the source file where your class is located. In most cases this should eliminate the need to write your own <code>__autoload($classname)</code> method.
To use MediaWiki's autoloading mechanism, you add entries to the {{ll|Manual:$wgAutoloadClasses|AutoloadClasses}} field.
The key of each entry is the class name; the value is the file that stores the definition of the class.
For a simple one class extension, the class is usually given the same name as the extension, so your autoloading section might look like this (extension is named ''MyExtension''):
<syntaxhighlight lang="json">
{
"AutoloadClasses": {
"MyExtension": "MyExtension_body.php"
}
}
</syntaxhighlight>
The filename is relative to the directory the extension.json file is in.
===Defining additional hooks===
See [[Special:MyLanguage/Manual:Hooks|Manual:Hooks]].
===Adding database tables===
{{mbox
| type = warning
| text = If your extension is used on any production WMF-hosted wiki please follow the [https://wikitech.wikimedia.org/wiki/Schema_changes Schema change guide].
}}
If your extension needs to add its own database tables, use the [[Special:MyLanguage/Manual:Hooks/LoadExtensionSchemaUpdates|LoadExtensionSchemaUpdates]] hook. See the manual page for more information on usage.
===Set up localisation===
See:
* [[#Localisation|Localisation (summary)]] or
* [[Special:MyLanguage/Localisation|Localisation (detailed)]]
===Add logs===
On MediaWiki, all actions by users on wiki are tracked for transparency and collaboration.
See [[Special:MyLanguage/Manual:Logging to Special:Log|Manual:Logging to Special:Log]] for how to do it.
{{anchor|Execution}}
== Execution ==
The technique for writing the implementation portion depends upon the part of MediaWiki system you wish to extend:
* '''Wiki markup:''' Extensions that extend wiki markup will typically contain code that defines and implements [[Special:MyLanguage/Manual:Tag extensions|custom XML tags]], [[Special:MyLanguage/Manual:Parser functions|parser functions]] and [[Special:MyLanguage/Manual:Variable|variables]].
* '''Reporting and administration:''' Extensions that add reporting and administrative capabilities usually do so by adding [[Special:MyLanguage/Manual:Special pages|special pages]]. For more information see [[Special:MyLanguage/Manual:Special pages|Manual:Special pages]].
* '''Article automation and integrity:''' Extensions that improve the integration between MediaWiki and its backing database or check articles for integrity features, will typically add functions to one of the many hooks that affect the process of creating, editing, renaming, and deleting articles. For more information about these hooks and how to attach your code to them, please see [[Special:MyLanguage/Manual:Hooks|Manual:Hooks]].
* '''Look and feel:''' Extensions that provide a new look and feel to MediaWiki are bundled into [[Special:MyLanguage/Manual:Skins|skins]]. For more information about how to write your own skins, see [[Special:MyLanguage/Manual:Skin|Manual:Skin]] and [[Special:MyLanguage/Manual:Skinning|Manual:Skinning]].
* '''Security:''' Extensions that limit their use to certain users should integrate with MediaWiki's own permissions system. To learn more about that system, please see [[Special:MyLanguage/Manual:Preventing access|Manual:Preventing access]]. Some extensions also let MediaWiki make use of external authentication mechanisms. For more information, please see [[Special:MyLanguage/AuthPlugin|AuthPlugin]]. In addition, if your extension tries to limit readership of certain articles, please check out the gotchas discussed in [[Special:MyLanguage/Security issues with authorization extensions|Security issues with authorization extensions]].
<!-- TODO: stuff about custom JS code, etc... -->
See also the '''[[Special:MyLanguage/Extensions FAQ|Extensions FAQ]]''', [[Special:MyLanguage/Developer hub|Developer hub]]
{{anchor|Localisation}}
== Localisation ==
{{mbox
| type = notice
| text = ''
* [[Special:MyLanguage/Localisation|Localisation]] – discusses the MediaWiki localisation engine, in particular, there is a list of features that can be localized and some review of the MediaWiki source code classes involved in localization.
* [[Special:MyLanguage/Manual:System message#Creating new messages|Creating new messages]]
* [[Special:MyLanguage/Localization checks|Localization checks]] – discusses common problems with localized messages
}}
('''Note''': While developing, you may want to disable both cache by setting $wgMainCacheType = CACHE_NONE and $wgCacheDirectory = false, otherwise your system message changes may not show up).
If you want your extension to be used on wikis that have a multi-lingual readership, you will need to add localisation support to your extension.
=== Store messages in ''<language-key>''.json ===
* Store message definitions in a localisation JSON-file, one for each language key your extension is translated in. The messages are saved with a message key and the message itself using standard JSON format. Each message id should be lowercase and may '''not''' contain spaces. An example you can find e.g. in extension [https://github.com/wikimedia/mediawiki-extensions-MobileFrontend/blob/master/i18n/de.json MobileFrontend]. Here is an example of a minimal JSON file (in this case ''en.json'':
''en.json''
<syntaxhighlight lang="json">{
"myextension-desc": "Adds the MyExtension great functionality.",
"myextension-action-message": "This is a test message"
}</syntaxhighlight>
=== Store message documentation in ''qqq''.json ===
The documentation for message keys can be stored in the JSON file for the pseudo language with code '''qqq'''. A documentation of the example above can be:
''qqq.json'':
<syntaxhighlight lang="json">{
"myextension-desc": "The description of MyExtension used in Extension credits.",
"myextension-action-message": "Adds 'message' after 'action' triggered by user."
}</syntaxhighlight>
=== Define messages ===
* Assign each message a <em>unique, lowercase, no space</em> message id; e.g., uploadwizard-desc
* For any text string displayed to the user, define a message.
* MediaWiki supports parameterized messages and that feature should be used when a message is dependent on information generated at runtime. Parameter placeholders are specified with $n, where n represents the index of the placeholder; e.g.
<syntaxhighlight lang="json">"mwe-upwiz-api-warning-was-deleted": "There was a file by this name, '$1', but it was deleted and you can not reupload the file. If your file is different, try renaming it."</syntaxhighlight>
=== Define message documentation ===
* Each message you define needs to have an associated message documentation entry [[Special:MyLanguage/Localisation#Message_documentation|Message_documentation]]; in '''qqq.json''' e.g.
<syntaxhighlight lang="json">"uploadwizard-desc": "Description of extension. It refers to [//blog.wikimedia.org/blog/2009/07/02/ford-foundation-awards-300k-grant-for-wikimedia-commons/ this event], i.e. the development was paid with this $300,000 grant."</syntaxhighlight>
=== Load the localisation file ===
* In your setup routine, define the location of your messages files (e.g. in directory '''i18n/'''):
<syntaxhighlight lang="json">
{
"MessagesDirs": {
"MyExtension": [
"i18n"
]
}
}
</syntaxhighlight>
=== Use wfMessage in PHP ===
* In your setup and implementation code, replace each literal use of the message with a call to <code>wfMessage( $msgID, $param1, $param2, ... )</code>. In classes that implement [[Special:MyLanguage/Manual:RequestContext|IContextSource]] (as well as some others such as subclasses of SpecialPage), you can use <code>$this->msg( $msgID, $param1, $param2, ... )</code> instead. Example:
<syntaxhighlight lang="php">
wfMessage( 'myextension-addition', '1', '2', '3' )->parse()
</syntaxhighlight>
=== Use mw.message in JavaScript ===
It's possible to use i18n functions in JavaScript too. Look at [[Special:MyLanguage/Manual:Messages API|Manual:Messages API]] for details.
{{anchor|Extension types}}
== Extension types ==
{{TNT|ExtensionTypes}}
Extensions can be categorized based on the programming techniques used to achieve their effect. Most complex extensions will use more than one of these techniques:
* '''Subclassing:''' MediaWiki expects certain kinds of extensions to be implemented as subclasses of a MediaWiki-provided base class:
**'''[[Special:MyLanguage/Manual:Special pages|Special pages]]''' – Subclasses of the [[SpecialPage.php|SpecialPage]] class are used to build pages whose content is dynamically generated using a combination of the current system state, user input parameters, and database queries. Both reports and data entry forms can be generated. They are used for both reporting and administration purposes.
**'''[[Special:MyLanguage/Manual:Skins|Skins]]''' – Skins change the look and feel of MediaWiki by altering the code that outputs pages by subclassing the MediaWiki class [[Special:MyLanguage/SkinTemplate|SkinTemplate]].
*'''[[Special:MyLanguage/Manual:Hooks|Hooks]]''' – A technique for injecting custom php code at key points within MediaWiki processing. They are widely used by MediaWiki's parser, its localization engine, its extension management system, and its page maintenance system.
*'''[[Special:MyLanguage/Manual:Tag extensions|Tag-function associations]]''' – [[w:XML|XML]] style tags that are associated with a php function that outputs HTML code. You do not need to limit yourself to formatting the text inside the tags. You don't even need to display it. Many tag extensions use the text as parameters that guide the generation of [[w:HTML|HTML]] that embeds google objects, data entry forms, RSS feeds, excerpts from selected wiki articles.
*'''[[Special:MyLanguage/Manual:Magic words|Magic words]]''' – A technique for mapping a variety of wiki text string to a single id that is associated with a function. Both [[Special:MyLanguage/Manual:Variable|variables]] and [[Special:MyLanguage/Manual:Parser functions|parser functions]] use this technique. All text mapped to that id will be replaced with the return value of the function. The mapping between the text strings and the id is stored in the array $magicWords. The interpretation of the id is a somewhat complex process – see [[Special:MyLanguage/Manual:Magic words|Manual:Magic words]] for more information.
** '''[[Special:MyLanguage/Manual:Variable|Variables]]''' – Variables are something of a misnomer. They are bits of wikitext that look like templates but have no parameters and have been assigned hard-coded values. Standard wiki markup such as [[Special:MyLanguage/Help:Variables|<code><nowiki>{{</nowiki>PAGENAME}}</code>]] or [[Special:MyLanguage/Help:Variables|<code><nowiki>{{SITENAME}}</nowiki></code>]] are examples of variables. They get their name from the source of their value: a php variable or something that could be assigned to a variable, e.g. a string, a number, an expression, or a function return value.
** '''[[Special:MyLanguage/Manual:Parser functions|Parser functions]]''' – <code><nowiki>{{</nowiki>''functionname'': ''argument 1'' | ''argument 2'' | ''argument 3''...}}</code>. Similar to tag extensions, parser functions process arguments and returns a value. Unlike tag extensions, the result of parser functions is [[w:wikitext|wikitext]].
* '''[[Special:MyLanguage/API:Extensions|API modules]]''' – you can add custom modules to MediaWiki's [[Special:MyLanguage/API:Action API|"action" web API]], that can be invoked by JavaScript, bots or third-party clients.
==Support other core versions==
You can visit the [[Special:MyLanguage/Manual:Extension support|extension support]] portal to keep on top of changes in future versions of MediaWiki and also add support for older versions that are still popular.
{{anchor|Licensing}}
== License ==
{{Extension/License}}
{{anchor|Publishing}}
== Publishing ==
To autocategorize and standardize the documentation of your existing extension, please see [[Template:Extension]]. To add your new extension to this Wiki:
{{Template:Extension/CreateExtensionInputBox}}
=== Deploying and registering ===
Consult [[Special:MyLanguage/Writing an extension for deployment|Writing an extension for deployment]]. If your extension adds namespaces, you may wish to register its [[Special:MyLanguage/Extension default namespaces|default namespaces]]; likewise, if it adds database tables or fields, you may want to register those at [[Special:MyLanguage/database table and field registration|database table and field registration]].
=== Help documentation ===
You should provide [[Special:MyLanguage/Project:PD help|public-domain help documentation]] for features provided by your extension. [[Special:MyLanguage/Help:CirrusSearch|Help:CirrusSearch]] is a good example. You should give users a link to the documentation via the [[Special:MyLanguage/Manual:Special pages#Help page|addHelpLink() function]].
== Providing support / collaboration ==
Extension developers should open an account on Wikimedia's [[Special:MyLanguage/Phabricator|Phabricator]], and [[Special:MyLanguage/Phabricator/Creating and renaming projects|request a new project for the extension]]. This provides a public venue where users can submit issues and suggestions, and you can collaborate with users and other developers to triage bugs and plan features of your extension.
== See also ==
* [[Special:MyLanguage/Extension:Example|Extension:Example]] – implements some example features with extensive inline documentation
** {{git repo |project=mediawiki/extensions/examples |text=examples git repo with this and other example code}}
* [[Special:MyLanguage/Extension:BoilerPlate|Extension:BoilerPlate]] – a functioning boilerplate extension, useful as a starting point for your own extension ({{Git repo |project=mediawiki/extensions/BoilerPlate |text=git repo}})
** ''Read'' the Example extension, ''base your own code on'' the BoilerPlate extension.
* [https://github.com/JonasGroeger/cookiecutter-mediawiki-extension cookiecutter-mediawiki-extension] – a template for the python tool cookiecutter to generate a boilerplate extension (with variables etc.)
** Allow you to get going quickly with your own extension. Can also generate the BoilerPlate extension.
* [[Special:MyLanguage/List of simple extensions|List of simple extensions]], copy specific code from them
* [[Special:MyLanguage/API:Extensions|API:Extensions]] – explains how your extension can provide an API to clients
* [[Special:MyLanguage/Manual:Extending wiki markup|Manual:Extending wiki markup]]
* [[Special:MyLanguage/Project:WikiProject Extensions|Project:WikiProject Extensions]]
* [[Special:MyLanguage/Manual:Coding conventions|Manual:Coding conventions]]
== References ==
<references />
[[Category:Extension creation{{translation}}|{{PAGENAME}}]]