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Typing about types of types

I am switching jobs and programming languages. I already follow a few Ruby oriented podcasts, but I was looking for some new ones. So in light of that search I just listened to an episode of Remote Ruby, the one with Adam Wathan. That seemed like an especially interesting one, because Adam is a Laravel PHP developer, which is what I am now.

Later on in the episode they of course talk about Tailwind, but they start with some very interesting things about PHP and the direction it's taking. Part of the things they say are things I heard said before, but a lot of the things are things I have thought myself and now heard back.

To summarize in my own words: PHP is moving more and more towards adding types and type annotations everywhere. They are not alone in this, types are hot: in the Javascript ecosystem Typescript is growing fast, and lots of other statically typed languages grow as well. But PHP's approach is a bit odd: there is no compile step with PHP, so all your errors are still runtime errors.

I really feel more at home in the Ruby world (and Laravel, as the home of the "PHP developers who want PHP to be like Ruby"), which is why switching to Ruby made sense. But it's also a bit scary to actually join the shrinking side of the world of programming. Ruby is so dynamic, I don't see it supporting type checking anytime soon.

On the other hand, I see the value of types. I think it's valid to say that computers are getting better and better at understanding programs, and types are an important part of how they do that. I like the idea of the friendly compiler and the promises of Elm. But should that mean my PHP-code has to be full of types everywhere? Only for more specific crashes on runtime?

It was nice to hear Adam talk about this other language called Crystal, which apparently does the complete opposite of PHP: compile with static types but with as minimal type declarations as possible. That made me realise even more that my problem might not be with types, but with these annotations everywhere.


While we're on the topic of types...

Also worth noting is Elixir's take on types. Elixir, like Erlang and Ruby, is dynamically typed, and due to the nature of the runtime it's actually very hard to create a type system for it. Some smart people tried it for Erlang and failed, but wrote an article about it and afterward created this tool called Dialyzer.

Dialyzer does not run on compilation, but more as a tool on the side, during development. It looks at your code (and, in Elixir, at the types you can optionally specify), and if it's certain that your code has an error, it will complain. This means it will not catch every bug there is to catch, which is nearly impossible in such a dynamic language (I have heard the article explains why), but it will still catch some and provide value that way.

To defend PHP a bit here: this looks a lot like how my type enthusiastic co-worker uses types in PHP. His Dyalizer is called PHPStorm, and like Dyalizer it runs analysis on the code during development. This also reduces the runtime errors in the same exact way.

The point where I get the creeps, however, is the place where the type is defined. In Elixir, it's an annotation you can optionally set on a function and in the compiled code remains no trace of this hint. In PHP, the type hints are baked into the language and cluttering the real code. And they are just not that good.

For example. In Elixir you can say "the thing this function returns is a Banana, please don't look at it". The function can then actually return a string, but once you access it as a string, Dialyzer will complain, because it's a Banana, you know. In PHP, there is only strings and integers, and if you want something for yourself you got to wrap it in an object. And before you know it, there's classes everywhere, that do not really add anything more than type information.


I am not the only PHP developer, and it seems like most PHP developers are happy with the direction that is taken. It's a bit sad that due to the way things are adopted, more and more libraries and thus applications are forced into using types. Although PHP says they are optional, because they are not optional when extending classes, type declarations leak into more and more PHP code.

It was also interesting hearing Adam talk about Ruby and especially calling out Elixir as one thing he would like to explore if PHP fails him. That was sort of my plan too, but I'm actually acting on it now. I am very curious how that will turn out.