Manual:ConvertExtensionToRegistration.php

Details
convertExtensionToRegistration.php is a maintenance script, which helps you migrating extensions and skins from PHP entry points to a JSON metadata file named or. If your extension supports older versions of MediaWiki, you should keep your PHP entry point until you drop support for those older versions.

Usage
This detects many variable declarations in the entry point and converts them into settings in an  file. Afterwards, you might still want to manually clean up these declarations inside the file and add a call to  as detailed on Manual:Extension registration#Migration for extension developers.