In early 2019, the PHP Framework Interoperability Group (PHP-FIG) released PSR-14, the Event Dispatcher specification. At the time I posted a long series of blog posts detailing PSR-14 in all its glory.
After discussing with a few other FIG folks, I've decided to release that blog series as a small ebook. Mainly that is to provide an easy single-point-of-reference for those who want to really understand PSR-14. Also, it serves as a simple fundraiser.
The book itself is available completely free, as the original blog posts were. However, you can also purchase a copy if you want to help support my work on the Framework Interoperability Group and Open Sourcing Mental Illness. OSMI is a non-profit organization that works to raise awareness of and research information about mental health challenges in the tech community. 50% of all royalties for this book are automatically donated to OSMI to support their vital work.
If you just want to grab a copy for free, go for it. If you are able to, though, I would encourage you to pay what you're comfortable with to support both my Open Source efforts and OSMI.