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 coreEdit

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 extensionsEdit

Configuration using extension.json (recommended)Edit

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 

In PHP, whenever you want your configuration values:

use MediaWiki\MediaWikiServices;
$config = MediaWikiServices::getInstance()->getConfigFactory()->makeConfig( 'yourextension' );
$user = $config->get( 'SomeConfigKey' );

If the prefix for your configuration keys is not the full extension name (e.g. is an abbreviation) 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. Generally this is a bad idea though, and will probably break the use of attributes.

Configuration using globalsEdit

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 prefixesEdit

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.


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 MediaWikiTestCase:

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

Upgrading from before MediaWiki 1.23Edit

MediaWiki version:

Starting with MediaWiki 1.23, there a new Config interface was introduced to access configuration options. This allowed us to abstract the backend in which we stored configuration options.

Pre-1.23 code would look like:

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

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 alsoEdit