Gain insights into functional programming in PHP. Learn about pure functions, immutable data, and monads. Explore error handling and apply principles through practical projects.

fp15aug.tar.gz

php7.4

ch8-phonebook

php8.1

purescript

python-pytoolz

chapter5-challenge1

AMQP

eris-testing-lesson

AMQP-Challenge

eris-testing-challenge

Functional programming is a paradigm that emphasizes expressing program logic as compositions of pure functions. PHP is a good fit for functional programming as functions are first-class citizens in its userland.
 
This course introduces you to the core concepts of functional programming, like pure functions, immutable data structures, and referential transparency. From there, you'll explore ways to handle errors with default values and callbacks while also exploring sum types such as Either or Maybe. Next, you'll look at functors before diving deep into monads, including IO, State, Reader, and List.
 
By the end of this course, you'll have a keen understanding of how to apply these principles in practice through a worked-out project. Not only will you know another way to program, but you’ll also feel confident enough to apply these ideas to your projects in PHP.

Learn Functional Programming in PHP

# Problem statement

In the “Temporal Coupling” lesson of this chapter, a PriceCalculator class was discussed to explain the concept. Later in the lesson, we resolved the issue of temporal coupling by immutability and showed how the constructor of the `PriceCalculator` and `computePrice` methods could be rewritten.

Now write the complete implementation of the  non-temporally coupled version of the same class.

# Requirements

The class's skeleton, along with its constructor's implementation, is given below. You only have to write code for the `computePrice` method using the `array_merge` and `array_map` functions.

> **Note:** To test your code, an object of the `PriceCalculator` class is instantiated with `$rates = ['USD' => 3 ,'EURO' => 6,'INR' => 10]`. Your provided implementation of the method will be tested against the object. 

# Sample input

```shell
$rates = ['USD' => 3 ,'EURO' => 6,'INR' => 10]
$items = [1,2,3,5]
```
# Expected output
```shell
$prices = [  [3,6,10],
             [6,12,20],
             [9,18,30],
             [15,18,50]
          ]
```

# Try it yourself

# Problem statement

In the “Temporal Coupling” lesson of this chapter, a PriceCalculator class was discussed to explain the concept. Later in the lesson, we resolved the issue of temporal coupling by immutability and showed how the constructor of the `PriceCalculator` and `computePrice` methods could be rewritten.

Now write the complete implementation of the  non-temporally coupled version of the same class.

# Requirements

The class's skeleton, along with its constructor's implementation, is given below. You only have to write code for the `computePrice` method using the `array_merge` and `array_map` functions.

> **Note:** To test your code, an object of the `PriceCalculator` class is instantiated with `＄rates = ['USD' => 3 ,'EURO' => 6,'INR' => 10]`. Your provided implementation of the method will be tested against the object. 

# Sample input

```shell
$rates = ['USD' => 3 ,'EURO' => 6,'INR' => 10]
$items = [1,2,3,5]
```
# Expected output
```shell
$prices = [  [3,6,10],
             [6,12,20],
             [9,18,30],
             [15,18,50]
          ]
```

# Try it yourself

Test your knowledge by writing code for a non-temporally coupled version of the PriceCalculator class.

Getting Started

An Introduction to Functional Programming in PHP

Core Concepts: Functional Programming in PHP

Composition and Helper Functions

Error Handling in Functional Programming

Functors in PHP

Parallelization of Tasks in PHP

Recursion, Pattern Matching, and Property Testing

Phonebook Application — A Simple Project

Conclusion

Appendix

Challenge 1: Remove Temporal Coupling

Problem statement