Much ado about null

Submitted by Larry on 13 May 2022 - 11:24am

null has a controversial history. It's been called "the billion-dollar mistake" by its creator. Most languages implement null, but those few that do not (such as Rust) are generally lauded for their smart design by eliminating a class of errors entirely. Many developers (myself included) have argued that code that uses null or nullable parameters/returns is intrinsically a code smell to be avoided, while others (also myself included, naturally) have argued that is too draconian of a stance to take.

Anna Filina has a very good three-part series (properties, parameters, and returns) on how to avoid null in PHP generally. Alexis King has a related post (excuse the Haskell) on how to avoid needing edge cases like null in the first place.

However, I want to go a bit deeper and try to understand null from a different angle, and tease out the nuance of why one would really want to use it, and thus what we should be doing instead. To get there we'll have to go through a tiny little bit of type theory, but it will be quick and painless, I swear.

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A robust, powerful, easy to use attribute parser for PHP

Submitted by Larry on 21 April 2022 - 4:56pm

After sitting on it for a while, I am pleased to release a PHP library for robust, powerful attribute handling in PHP 8.1: Crell/AttributeUtils. It's a robust, centralized tool for slicing, dicing, and reverse engineering classes in PHP using attributes.

The basics

The basic model of Attribute Utils is to analyze a class "with respect to" some attribute. That attribute may be defined on the class, or not. (Both options have meaning.) That attribute may be associated with attributes on properties or methods, which are all scanned together to produce a picture of a class.

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PHP Tricks: Multi-value match()

Submitted by Larry on 19 April 2022 - 11:41am

Last time, I talked about fun uses of the match() expression in PHP, using unconventional types of expressions on the right-arm branch. This time, I want to expand that discussion to include fun tricks on the left-side of the `=>`, and how you can easily match by multiple values at the same time.

I'm going to assume you have read the previous installment about how match() works and what an "expression" means. Also, I don't claim to be the original source of these tricks. I'm just documenting them because they're cool. Let's dive in.

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PHP Tricks: Uncommon match() expressions

Submitted by Larry on 15 April 2022 - 1:15pm

Recently, I've been helping a new developer out in a chat room. He's still learning PHP and working through tutorials, with lots of questions along the way. Earlier this week, by accident, he stumbled across a use of match() statements I'd not considered before. While technically not right for his use case, it did suggest another, potentially valid use for match() I'd not seen. Let's add it to the list of cool things you can do with match().

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PHP Tricks: Access control bypass

Submitted by Larry on 16 March 2022 - 1:15pm

This is old-hat to some people, but it's still a nice trick.

PHP has long supported Java-esque property and method access control. Object properties and methods may be marked public, protected, or private to control what other code may access them. The general recommendation for years is that properties should be non-public in almost all cases, unless you're using the new readonly flag in PHP 8.1.

(There's a good case to be made that object-level encapsulation is the wrong model in the first place, and package-level visibility is the superior model. I happen to agree with that argument, but that's neither here nor there for the time being.)

Most of the time, you want to respect the visibility set by the code's author. It's telling you how an object should be used, and if you do otherwise you're on your own. However, there are cases in meta-programming situations where you need to be able to bypass the visibility in order to manipulate the state of an object in a dynamic fashion. The most common scenarios are serialization, de-serialization, hydration from an ORM, and similar.

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Advent of Functional PHP: Review

Submitted by Larry on 29 December 2021 - 7:10pm

Over the last few weeks, I've been following Advent of Code 2021, using Functional PHP as an approach. It's been a fun and educational process, at least for me and apparently for a few other people, at least given how popular the articles have been.

For reference, the full list of articles in this series is here:

Advent of Functional PHP: Day 10

Submitted by Larry on 24 December 2021 - 7:14pm

For the 10th Day of Advent of Code, we're asked to solve a matching braces problem. This is a common parser exercise, but it's made a bit more complex in this case by using multiple types of braces. Specifically, we're handling a series of lines that contain ( and ), but also < and >, [ and ], and { and }.

The story jazzes it up as being the code of our submarine's navigational computer, which consists entirely of braces in a sort of eldritch horror version of brainfuck, but that's mostly just a distraction.

Advent of Functional PHP: Day 9

Submitted by Larry on 23 December 2021 - 11:21am

Day 9 of this year's Advent of Code revolves around grid interpretation. Specifically, we are given a grid of numbers and want to find the low points, that is, the numbers that are smaller than any of their orthogonal neighbors. (We're told to ignore diagonals in part 1.)

After finding the low points, we need to do a bit of math on each one, and add them up. As usual, this last step is mostly just to produce a single verification number at the end. That part is easy as usual, but how do we find the low points?

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Advent of Functional PHP: Day 8

Submitted by Larry on 20 December 2021 - 10:06am

Advent of Code Day 8 was, to put it mildly, a pain in the ass. There's a couple of reasons for that. It's a naturally tricky problem, it's hard to genericize, and it's explained fairly badly. It took a while but with some help from others I was finally able to figure out (and refactor to) a good, functional solution to it. So let's dive in.

The problem boils down to one of encryption. Our input is several lines that all look like this:

acedgfb cdfbe gcdfa fbcad dab cefabd cdfgeb eafb cagedb ab | cdfeb fcadb cdfeb cdbaf

Where each letter corresponds to one segment in an LED display for a number. Each number appears once on the left side, which is enough for you to figure out what letter corresponds to what segment. Then we need to use that knowledge to decode the numbers on the right and figure out what the number is.

Advent of Functional PHP: Day 7

Submitted by Larry on 7 December 2021 - 3:38pm

Advent of Code Day 7 this year is another problem that's more about the math than about the programming, so we won't see much in the way of new functional techniques. Still, there's some interesting bits in there.

Today we need to calculate the fuel costs of moving a bunch of crabs in submarines all into a line. (Don't ask. Really, don't ask.) Essentially we want to center-align a series of points using the least "cost" possible. Crab positions are represented by a single number, as crabs can only move horizontally. (Because crabs.)

The trick for today is realizing that the crabs don't matter; it's a distance-cost calculation. In part 1, the cost for a crab to move one space toward whatever alignment number we want to pick is 1.

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