Manual:Configuration for developers

For documentation about configuring MediaWiki, see Manual:Configuration .

This is a guide for core and extension developers about creating and accessing configuration settings.

For core

To access a configuration variable such as $wgFoo:

$config = $this->getConfig(); // this is a Config object
$foo = $config->get( 'Foo' );

If you don't have access to any ContextSources, you can get a Config object with

$config = MediaWikiServices::getInstance()->getMainConfig();

This should not be used to fetch global variable objects such as $wgUser or $wgRequest .

For extensions

Configuration using extension.json (recommended)

Main page: Manual:Extension registration#Configs (Your extension/skins settings)

Extensions that have an extension.json file should set up configuration variables as described in this section.

If your extension is called YourExtension, in extension.json you'd write:

{
	"config": {
		"YourExtensionSomeConfigKey": {
			"value": "SomeValue",
			"description": "The description for the configuration",
		}
	},
	"ConfigRegistry": {
		"yourextension": "GlobalVarConfig::newInstance"
	},
	"manifest_version": 2 
}

Naming conventions:

• It is highly recommended to start the name of the configuration key with the name of your extension (as in the example), to ensure the config key is unique among all keys of all applications. Not doing this is a bad idea, and will probably break the use of attributes.
• It is customary to make the name for the ConfigRegistry, here "yourextension", lowercase and without spaces.

Custom prefixes

If the prefix for your configuration keys is not the default "wg", you can specify it with the config_prefix or _prefix key, depending on the schema version (see docs). You should make sure it doesn't collide with any existing extension.

Retrieve configuration option

In PHP, whenever you want your configuration values, you can write:

use MediaWiki\MediaWikiServices;
$config = MediaWikiServices::getInstance()->getConfigFactory()->makeConfig( 'yourextension' );
$myConfigOption = $config->get( 'YourExtensionSomeConfigKey' ); // without prefix!

If the above does not work, you can call it as a global:

global $wgYourExtensionSomeConfigKey;

Configuration using globals

If you can, use the extension.json file for configuration (see above). If you can't, use this snippet (only works with wg prefixed variables):

$wgConfigRegistry['yourextension'] = 'GlobalVarConfig::newInstance';

// Now, whenever you want your config object
$config = ConfigFactory::getDefaultInstance()->makeConfig( 'yourextension' );

Custom prefixes

In the past, some extensions used "eg" instead of "wg". We want to move away from prefixes, but you can still continue to use them:

// In your extension's setup file (ExtName.php)
wfExtNameConfigBuilder() {
	return new GlobalVarConfig( 'eg' ); // replace "eg" with whatever your custom prefix is
}
$wgConfigRegistry['ext-name'] = 'wfExtNameConfigBuilder';

If you use extension registration, there is a prefix or config_prefix (depending on the schema version) field you can use instead.

Testing

When debugging, you use the following to test that you are accessing the right Config instance. You should do this in place of the $wgConfigRegistry shown in the for extensions section above.

$wgConfigRegistry['ext-name'] = function() { 
	return new HashConfig( array( 
		// Array of config variables and values
		'Foo' => 'baz'
	) );
};

If you are accessing the wrong Config instance, a ConfigException will be produced.

For modifying configuration variables in PhpUnit tests in extensions using manifest version 1 (or in MediaWiki core), you can do the following in test cases that extend MediaWikiIntegrationTestCase:

$this->setMwGlobals( [ 'wgFoo' => 'baz' ] );

Programmatically modifying configuration values

The only Config implementation that supports modification of values is HashConfig, which is mostly used in tests.

One way to modify values from the MainConfig service is via the MediaWikiServices hook, but this is discouraged. Instead, a hook should be used to allow more controlled and explicit modification of the relevant values.

Upgrading from before MediaWiki 1.23

MediaWiki version:

≥ 1.23

In MediaWiki 1.23 a new Config interface was introduced to access configuration options. This allowed us to abstract the backends in which we store configuration options.

Pre-1.23 code would look like:

class ApiMyModule extends ApiBase {
	public function execute() {
		global $wgFoo;
		if ( $wgFoo ) {
			// do stuff
		}
	}
}

Tracked in Phabricator
Task T71084

1.23+ code should look like this:

class ApiMyModule extends ApiBase {
	public function execute() {
		$config = $this->getConfig(); // this is a Config object
		if ( $config->get( 'Foo' ) ) {
			// do stuff
		}
	}
}

You'll notice a few changes here:

• We use $this->getConfig() to get the default Config object. Most contexts implement getConfig().
• Rather than checking for "wgFoo", you ask the Config object for "Foo", without any wg prefix.

See also

• Manual:$wgConfigRegistry
• Manual:Config.php
• Legoktm's presentation at the 2015 MediaWiki Developer Summit