Functional PHP (2017)
Chapter 1. Functions as First Class Citizens in PHP
Chapter 2. Pure Functions, Referential Transparency, and Immutability
Chapter 3. Functional Basis in PHP
Chapter 4. Composing Functions
Chapter 5. Functors, Applicatives, and Monads
Chapter 7. Functional Techniques and Topics
Chapter 9. Performance Efficiency
Chapter 10. PHP Frameworks and FP
Chapter 11. Designing a Functional Application