PHP

The case for partials and pipes in PHP

The Partial Function Application RFC is currently in voting, and right now it's a close vote to the negative. I wanted to take this opportunity to try and make the broader case for partial application and for its related RFC, the pipe operator, in a way that is more appropriate for a blog post than the RFC body (which is, by design, more concerned with the finer details of "what").

The main pushback on the RFC so far is that the benefits don't outweigh the cost of yet-more-syntax in the language. Which is a fair position to hold, albeit one I hope to convince you is incorrect. That is, I believe the benefits vastly outweigh the syntax and implementation cost.

Continue reading this post on PeakD.

Larry 23 June 2021 - 3:07pm

Good technical writing is hard

Submitted by Larry on 31 May 2021 - 8:07pm

A few days ago, I randomly tossed this out on Twitter without context:

Technical writing requires assuming the reader is simultaneously highly intelligent and utterly ignorant, without making them feel like you think they're utterly ignorant.

That shit is hard, yo.

Someone asked for ideas on how to achieve that goal, and it seemed like a topic worthy of discussion so here we are.

Technical writing is not for Dummies

I would expand the statement above a bit, actually. Good technical writing requires:

One year of functional PHP; now in Russian!

Submitted by Larry on 11 May 2021 - 8:14pm

A year ago, I published my first solo book, Thinking Functionally in PHP. The reception has been extremely positive; almost everyone that's read it (that has bothered to talk to me about it) has found it clear, helpful, and enlightening. Mission accomplished!

To celebrate the one year anniversary of the book's publication, I am happy to make two announcements.

First, Thinking Functionally in PHP is now available in Russian! The translation is by Alexey Pyltsyn, who is responsible for the Russian translation of the PHP documentation as well as numerous other tech book translations.

I made a TYPO

Submitted by Larry on 5 May 2021 - 4:55pm

I am a firm believer in "anything worth doing is worth doing right." So when given the opportunity to get paid to do that, it's hard for me to say no. Which is why I didn't.

I am happy to report that this is my first week in my new role as Staff Engineer on the TYPO3 core contributors team.

Continue reading on PeakD.

Object properties, part 2: Examples

Submitted by Larry on 9 January 2021 - 6:33pm

In my last post, I went over some of the pros and cons of various proposals for making PHP objects more immutable-ish, and the contexts in which they would be useful. I also posted the link to the PHP Internals list, where it generated some interesting if meandering discussion (as is par for the course on Internals).

One of the requests was for sample code to demonstrate why I felt particular feature proposals were better than others. Fair enough! This post is in response to that request, and I think it will help illuminate the challenges better.

For this exercise, I chose to experiment with a junior version of the PSR-7 request object as a concrete example. The code below is not exactly PSR-7; it's a representative sample of portions of a naive, slightly reduced scope version of PSR-7 requests only, and using all PHP 8.0 features available. The goal is not a complete working object, but sufficient real-world representative examples of situations that an immutability plan would need to address.

Continue reading this post on PeakD.

Object properties and immutability

Submitted by Larry on 28 December 2020 - 5:30pm

There has been much discussion in recent weeks in PHP circles about how to make objects more immutable. There have been a number of proposals made either formally or informally that relate to object property access, all aimed at making objects safer through restricting write access in some way.

Since my last mega post on PHP object ergonomics was so well-received and successful (it resulted in both constructor promotion and named arguments being added to PHP 8.0, thanks Nikita!), I figure I'll offer another summary of the problem space in the hopes of a deeper analysis suggesting a unified way forward.

Continue reading on PeakD

Byte-sized functional programming: Composition over inheritance for functions, too

Submitted by Larry on 15 August 2020 - 10:07am

A popular refrain in object-oriented code is to favor object composition over inheritance. It offers more flexibility, less overhead, and ends up being easier to reason about. The same concept applies to functions, too!

A common pattern is to have a function that does some work and then calls another function, which does some work and calls another function, and so on. The problem is that the first function then cannot be used or tested without the entire chain of other functions it calls. This is the function equivalent of "inheritance."

Instead, we can compose functions, that is, pipe them together. Instead, take the output of the first function and pass it to the second, then take the second's output and pass it to the third, etc. That way, each of the functions can be reused, tested, and understood in isolation, then we can stick them together like LEGO blocks to build whatever series of steps we want.

That is, instead of this:

<?php
function A($in)
{
  
// ...
  
return B($out);
}

function

B($in)
{
  
// ...
  
return C($out);
}

function

C($in)
{
  
// ...
  
return $out;
}
?>

Structure it like this:

<?php
function A($in)
{
   
// ...
   
return $out;
}

function

B($in)
{
   
// ...
   
return $out;
}

function

C($in)
{
   
// ...
   
return $out;
}

function

doit($in) {
   
$out = A($in);
   
$out = B($out);
   
$out = C($out);
    return
$out;
}
?>

Now `A()`, `B()`, and `C()` are all easier to read, understand, and test, and we can more easily add a step B2 or D if we want. So powerful is this concept that many languages have a native operator for piping functions together like that. PHP doesn't, yet, but it's straightforward enough to do in user space anyway.


Want to know more about functional programming and PHP? Read the whole book on the topic: Thinking Functionally in PHP.


Thinking Functionally in PHP

Byte-sized functional programming: Filter first

Submitted by Larry on 3 August 2020 - 1:47pm

Often when working with a list, we only want to work with a subset of a list that meets some criteria. All non-zero values, for example, or all users that have a given role. The procedural way to do that is to stick an if statement inside a foreach loop:

<?php
foreach ($list as $value) {
    If (!
meets_criteria($value)) {
        continue;
    }
   
// ...
}
?>

That mixes up the filtering with the iteration, though. It also doesn't work if we're using `array_map()`.

Instead, we can make stripping down the list a separate operation called "filter." PHP offers the array_filter() function for that purpose.

<?php
$criteria
= fn(User $user): bool => $user->hasRole('moderator');

$filtered = array_filter($users, $criteria);
?>

Now we can work with the `$filtered` list, which has only the values we want. That could be a simple foreach<code> loop, or, better, it's now ideally suited for use with <code>array_map().


Want to know more about functional programming and PHP? Read the whole book on the topic: Thinking Functionally in PHP.


Thinking Functionally in PHP

Byte-sized functional programming: Mapping out your data

Submitted by Larry on 27 July 2020 - 3:42pm

Procedural code tends to think in terms of writing out steps, and so the usual way to work with a list is to iterate it using a `for` or `foreach` loop.

Functional code tends to think in terms of the relationships and transformations between data, where those relationships and transformations are defined as functions. That means the natural way to work with a list is to define a function that is the relationship between one list and another. The most common way of doing that is with a "map," which in PHP usually means the `array_map()` function.

With `array_map()`, you give it an array and a function. You get back the result of applying that function to every element in the array, individually. Like so:

<?php
$arr
= [1, 2, 3, 4, 5];
$fun = fn($x) => $x * 2;
$result = array_map($fn, $arr);
?>

The advantages of that over a `foreach` loop are:

* The function is a separate operation that can be as complex as you want.
* If it's more than a line or two, make it its own function or method somewhere and test it in isolation.
* If it's trivial, you can simply inline it.
* It's clear, visually, that every element's transformation is independent of every other's, because that's how `array_map()` works. A `foreach` loop may maintain state from one iteration to the next, but `array_map()` does not.


Want to know more about functional programming and PHP? Read the whole book on the topic: Thinking Functionally in PHP.


Thinking Functionally in PHP

Byte-sized functional programming: Immutable variables are easier to understand

Submitted by Larry on 21 July 2020 - 7:30am

An immutable variable is one whose value doesn't change after it has been first set. PHP doesn't natively support that, but we can write our classes in such a way to simulate it. For example, rather than this:

<?php
class Point
{
   private
int $x;
   private
int $y;
 
   public function
__construct(int $x, int $y)
   {
      
$this->x = $x;
      
$this->y = $y;
   }
 
   public function
moveUp(int $by): void
  
{
      
$this->y += $by;
   }
}
?>

We can write this:

<?php
class Point
{
   private
int $x;
   private
int $y;
 
   public function
__construct(int $x, int $y)
   {
      
$this->x = $x;
      
$this->y = $y;
   }

   public function

moveUp(int $by): Point
  
{
      
$new = clone ($this);
      
$new->y += $by;
       return
$new;
   }
}
?>

In the second version, once a given `Point` object is created it will never change. We can safely pass it to another function or method and be guaranteed that its value won't change without us knowing. Instead, any attempt to change it results in a new object, with its own identity, representing the new point in space. (In practice there would be other methods here as well, but we're focusing on just the mutation part.)

Code that uses immutable variables is easier to think about, because we don't have to worry about "does passing this object to this function change it?" We know it doesn't. Once we know something about an object we can guarantee that fact doesn't change. That can make a lot of subtle bugs impossible, which means we don't have to spend time looking for or correcting them.


Want to know more about functional programming and PHP? Read the whole book on the topic: Thinking Functionally in PHP.


Thinking Functionally in PHP