Extensions provide a way to group related parsers, renderers, etc. together with pre-defined priorities, configuration settings, etc. They are perfect for distributing your customizations as reusable, open-source packages that others can plug into their own projects!

To create an extension, simply create a new class implementing ExtensionInterface. This has a single method where you’re given a ConfigurableEnvironmentInterface to register whatever things you need to. For example:

final class EmojiExtension implements ExtensionInterface
    public function register(ConfigurableEnvironmentInterface $environment)
            ->addInlineParser(new EmojiParser(), 20)
            ->addInlineRenderer(Emoji::class, new EmojiRenderer(), 0)

To hook up your new extension to the Environment, simply do this:

$environment = Environment::createCommonMarkExtension();
$environment->addExtension(new EmojiExtension();

$converter = new CommonMarkConverter([], $environment);
echo $converter->convertToHtml('Hello! :wave:');