Yesterday I released Services_Linkback in version 0.3.0. It is a PHP library that provides you with everything needed to send and receive webmentions and pingbacks - which are mainly used to notify blogs about new comments on posts.
Services_Linkback is now installable via composer, and all dependencies are also available on packagist now. The HTTP2 package was the last that I had to bring on packagist for that.
Apart from the eased installation, the library got a couple of bug fixes that make it pass all the discovery tests on webmention.rocks! On the single test pages like Discovery Test #2 you will find test comments made via commentpara.de, which uses Services_Linkback for notification sending.