Summary: Functors in PHP

Review what we’ve learned about functors and monads in this chapter.

We'll cover the following
  • The fundamentals of functors and monads can be traced to category theory: a subscience whose primary concern is composition.

  • Categories are connections of objects and arrows, which, in programming, can be encoded as types and functions.

  • Functors are fundamentally meta-categories that map one category onto another while keeping all category properties intact. This property characterizes the map operation in the programmatic design and use of functors.

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