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

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ch8-phonebook

php8.1

purescript

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AMQP

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AMQP-Challenge

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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

# Multiprocessing or multithreading?

Not to be confused with multithreading, **multiprocessing** is another concurrency technique with the fundamental idea of processing tasks in parallel by spawning new processes with unique process identifiers and memory allocations. Achieving task parallelization through multiprocessing is possible through an Inter-Process Communication (IPC) facilitated by signals, or asynchronous Unix-system based notifications analogous to interrupts. As is the case with threading, PHP isn’t built to extensively support multiprocessing which, like threading, is contingent on an understanding of Operating System deficiencies and limitations.



# Multiprocessing in PHP

Because multiprocessing in PHP is heavily reliant on signals, it follows that the shortcomings of signal-based IPC impact the success of multiprocessing. PHP has a multiprocessing utility in the form of an extension named PCNTL with potencies that are reflective of similar routines existent in the C language, or the PHP progenitor.

## The PCNTL extension

**PCNTL**, short for **Process Control**, is a genealogy of functions premised on the forking concept, which is ever-present in Unix-based systems. **Forking** emphasizes the creation of appendages of parent processes, befittingly named child processes, whose decomposability semantics are at the discretion of the creator.

The PCNTL extension for PHP is bundled into the PHP userland by default on Linux-based operating systems. It’s not suitable for Windows, because Windows does not have support for signals. The Windows Subsystem for Linux, however, provides a favorable runtime for Unix utilities, including those built into PHP.

### A Brief Note About the WSL

> **Note:** The **Windows Subsystem for Linux (WSL)** is a Microsoft utility with the purpose is to offer the capabilities of Linux systems to Windows Operating System users. It, therefore, holds that the Linux installation process is possible in a Windows environment, a WSL environment. Chief among the advantages of the subsystem are the usage of one file system and interoperability of installable Linux and Windows dependencies. A comprehensive guide on installing the subsystem exists on the Microsoft 

## The task

To demonstrate the potency of forking is a simple script, the purpose of which is to parallelly compute the Fibonacci numbers that correspond to the numbers in a list. The snippet below utilizes the PCNTL extension’s forking capabilities to create forks (child processes) for each argument, in this case, a number, to generate a corresponding Fibonacci value.

Learn about multiprocessing in PHP and PCNTL extension.

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

Multiprocessing in PHP

Multiprocessing or multithreading?