Larry Garfield's Post

If you're on here, I assume you are interested in PHP. If you're interested in PHP, you should be interested in functional programming in PHP.

In that case, you should check out "Thinking Functionally in PHP", the most gentle introduction to functional programming you'll ever find, and written in your favorite language! (English, although a Russian version is also available.)

https://leanpub.com/thinking-functionally-in-php/