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 previous lesson, we eliminated exceptions by rewriting the `authenticateUser` function as a two-track Either monad-based function.

This time, you have to rewrite the function featured there to utilize Maybe monad case analysis.

# Requirements

By maintaining all the requirements stated in the previous challenge, you have to perform the following additional requirement in order to complete the challenge:

* Convey each error message as an array with the `error` key by using the Maybe monad.

To reiterate, the requirements were:
1. If the provided `username` is not valid, then the associative array returned by the function must be:

    `error => Sorry, your username is invalid`.

2. If the provided `password` is not valid, the associative array returned by the function must be:

    `error => Sorry, your password is invalid`.

3. If both—the provided `username` and `password`—are valid, then the function will perform the following tasks:

    * Add a new field with the name `role` in `USER_DATA`, whose value is either `admin` or `customer` depending on the value of the `admin` key (`true` for the admin and `false` for the customer).

    * Remove the password from the resultant data.

> **Note:** Unlike the first two constraints, you are'nt required to return a custom string for this one. The test cases for this challenge will automatically verify whether these two tasks are performed on `USER_DATA` or not.
    > - Actual username: `kelly92`
    > - Actual password: `trap_223`

# Sample inputs and outputs

## Sample input 1
```
Username = "kellys92"
Password = "trap_223"
```
## Expected output
```String
[error] => Sorry, your username is invalid
```

## Sample input 2
```
Username = "kelly92"
Password = "trap223"
```
## Expected output
```String
[error] => Sorry, your password is invalid
```

> **Note:** The code from the solution tab of the previous challenge can be found #concept=UntitledConcept2# here #concept#.

Test your knowledge by writing code to convey error messages as an array using the Maybe monad.

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 2: Error Messages Using Maybe Monad

Problem statement

Requirements