Feature Toggles

TYPO3 provides an API class for creating so-called 'Feature Toggles'. Feature toggles provide an easy way to add new implementations of features next to their legacy version. By using a feature toggle, the integrator or site admin can decide when to switch to the new feature.

The API checks against a system-wide option array within $GLOBALS['TYPO3_CONF_VARS']['SYS']['features'] which an integrator or admin can set in the LocalConfiguration.php file. Both TYPO3 Core and Extensions can provide alternative functionality for a certain feature.

Examples for features are:

  • Throw exceptions in new code instead of just returning a string message as error message.
  • Disable obsolete functionality which might still be used, but slows down the system.
  • Enable alternative PageNotFound handling for an installation.

Naming of Feature Toggles

Feature names should NEVER be named "enable" or have a negation, or contain versions or years.

Bad examples:

  • enableFeatureXyz
  • disableOverlays
  • schedulerRevamped2018
  • useDoctrineQueries
  • disablePreparedStatements
  • disableHooksInFE

Good examples:

  • ExtendedRichtextFormat
  • NativeYamlParser
  • InlinePageTranslations
  • TypoScriptParserIncludesAsXml
  • NativeDoctrineQueries

Using the API as extension author

For extension authors, the API can be used for any custom feature provided by an extension:

if (GeneralUtility::makeInstance(Features::class)->isFeatureEnabled('myFeatureName')) {
   // do custom processing
}

The name can be any arbitrary string, but an extension author should prefix the feature with the extension name as the features are global switches which otherwise might lead to naming conflicts.

Core Feature Toggles

Some examples for feature toggles in the TYPO3 Core:

  • redirects.hitCount: Enables hit statistics in the redirects backend module
  • TypoScript.strictSyntax: If on, TypoScript is parsed in strict syntax modes. Enabling this feature means old condition syntax (which is deprecated) will trigger deprecation messages.

Enable / Disable Feature Toggle

Features can be toggled in the Settings module via Feature Toggles:

../../_images/FeatureToggles.png

Internally, the changes are written to LocalConfiguration.php:

'SYS' => [
   'features' => [
      'redirects.hitCount' => true,
   ],
]