Transcript

Derick Rethans 0:15

Hi I'm Derick. Welcome to PHP internals news, a podcast dedicated to explaining the latest developments in the PHP language. This is episode 81. Today I'm talking with Matt Brown, the author of Psalm and Ondřej Mirtes, the author of PHPStan, about an RFC that I propose to alter the noreturn type. Matt, would you please introduce yourself?

Matthew Brown 0:37

Hi, I'm Matthew Brown, Matt, I live in New York, I'm from the UK. I work at a company called Vimeo, and I've been working with for the past six years on a static analysis tool called Psalm, which is my primary entry into the PHP world, and I, along with Ondřej authored this noreturn RFC.

Derick Rethans 1:01

Alright Ondřej, would you please introduce yourself too?

Ondřej Mirtes 1:04

Okay, I'm Ondřej Mirtes, and I'm from the Czech Republic, and I currently live in Prague or on the suburbs of Prague, and I've been developing software in PHP for about 15 years now. I've also been speaking at international conferences for the past five years before the world was still alright. In 2016, I released PHPStan, open source static analyser focused on finding bugs in PHP code basis. And somehow, I found a way to make a living doing that so now I'm full time open source developer, and also father to two little boys.

Derick Rethans 1:35

Glad to have you both here. We're talking about something that clearly is going to play together with static analysers. Hence, I found this quite interesting to see to have two competitive projects, or are the competitive, or are the cooperative.

Matthew Brown 1:56

I think half and half.

Derick Rethans 1:57

Half and half. Okay.

Ondřej Mirtes 1:59

Competition is a weird concept in open source where everything is released for free here that

Derick Rethans 2:04

That's certainly true, but you said you're making your living out of it now so maybe there was something going on that I'm not aware of. In any case, we should probably chat about the RFC itself. What's the reason why you're wanting to add to the noreturn type?

Ondřej Mirtes 2:18

I'm going to start with a little bit of a detour, because in recent PHP development, it has been a trend to add the abilities to express various types natively, in in the language syntax. These types, always originally appeared in PHP docs for documentation reasons, IDE auto completion, and later were also used, and were being related with static analysis tools. This trend of moving PHP doc types tonight this type started probably with PHP seven that added scalar type hint. PHP 7.1 added void, and nullable type hints, 7.2 added object type, 7.4 added typed properties. And finally, PHP, 8.0 added union types. Right now to PHP community, most likely waits for someone to implement the generics and intersection types, which are also widely adopted in PHP docs, but there's also a noreturn, a little bit more subtle concept, that would also benefit from being in the language. It marks functions and methods that always throw an exception, or always exit, or ent

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Transcript

Derick Rethans 0:14

Hi I'm Derick, welcome to PHP internals news, the podcast dedicated to explain the latest developments in the PHP language. This is episode 80. In this episode I speak with Nikita Popov again about another RFC that he's proposing. Nikita, how are you doing today?

Nikita Popov 0:30

I'm still doing fine.

Derick Rethans 0:33

Well, that is glad to hear. So the reason why you saying, I'm still doing fine, is of course because we basically recording two podcast episodes just behind each other.

Nikita Popov 0:41

That's true.

Derick Rethans 0:42

If you'd be doing fine 30 minutes ago and bad now, something bad must have happened and that is of course no fun. In any case, shall we take the second RFC then, which is titled static variables in inherited methods. Can you explain what is RFC is meant to improve?

Nikita Popov 1:00

I'm not sure what this meant to improve, it's more like trying to fix a bug, I will say. This is a really, like, technical RFC for an edge case of an edge case, so I should say first, when I'm saying static variables, I'm not talking about static properties, which is what most people use, but static variables inside functions. What static variables do unlike normal variables, is that they persist across function calls. For example, you can have a counter static $i equals zero, and then increment it, and then each time we call the function, it gets incremented each time and the value from the previous call is retained. So that's just the context of what we're talking about.

Derick Rethans 1:43

Why would people make use of static variables?

Nikita Popov 1:46

I think one of the most common use cases is memoization.

Derick Rethans 1:50

Can you explain what that is?

Nikita Popov 1:51

If you have a function that that computes some kind of expensive result, but which is always the same, then you can compute it only once and store it inside the static variable, and then return it. Maybe possibly keyed by by the function arguments, but that's the general idea. And this also works if it's a free standing function. So if it's not in the method where you could store state inside the static property or similar, but also works inside a non method function.

Derick Rethans 2:22

The keyword here in his RFC's title is inherited methods, I suppose. What happens currently there?

Nikita Popov 2:29

There are a couple of issues in that area. The key part is first: How do static variables interact with methods at all? And the second part is how it interacts with inheritance. So first if you have an instance method, with a static variable, then some people expect that actually each object instance gets a separate static variable. This is not the case. The static variables are really bound to functions or methods, they do not depend on the object instanc

Transcript

Derick Rethans 0:14

Hi, I'm Derick. Welcome to PHP internals news, a podcast dedicated to explain the latest developments in the PHP language. As you might have noticed, the podcasts are currently not coming out once every week, as there are not enough RFCs being submitted for weekly episodes. I suspect that this will change soon again. This is episode 79. In this episode, I speak with Nikita Popov, about a few more language additions that he's proposing. Nikita, how are you doing today?

Nikita Popov 0:43

I'm doing well, Derick, how are you doing?

Derick Rethans 0:45

I'm pretty good as though, I always much happier when it's sunny outside.

Nikita Popov 0:48

Yeah, for us to weather also turned today. Yesterday it was still cold.

Derick Rethans 0:53

We're here to talk about a few RFCs. The first one, titled "New in Initializers". What is this RFC about?

Nikita Popov 1:00

The context is that PHP has basically two types of expressions: ones, the ones used on normal code, and the other one in a couple of special places. These special places include parameter default values, property default values, constants, static variable defaults, and finally attribute arguments. These don't accept arbitrary expressions but only a certain subset. So we call those usually constant expressions, even though they are not maybe constant in the most technical sense. The differences really that these are evaluated separately so they don't run on the normal PHP virtual machine. There is a separate evaluator that basically evaluates an abstract syntax tree directly. They are just like, have different technical underpinnings.

Derick Rethans 1:49

Because it is possible to for example, define a default value to seven plus 12?

Nikita Popov 1:54

Exactly. It's possible to define it to seven plus 12, but maybe not to seven plus variable A, or seven plus some function call or something like that.

Derick Rethans 2:03

I guess the RFC is about changing this so that you can do things like this. What are you proposing to add?

Nikita Popov 2:09

Yes, exactly. So my addition is a very small one, actually. I'm only allowing a single new thing and that's using new, so you can use new, whatever, as a parameter default, property default, and so on.

Derick Rethans 2:23

In this new call, pretty much a constructor call for a class of course, can arguments to be dynamic, or do they need to be constant as well?

Nikita Popov 2:33

Rules are always recursive, so you can like pass arguments to your constructor, but they also have to follow the usual rules. So again, they also have to be constant expressions, or after this RFC, they can also include new, but they cannot include variable references and so on.

Derick Rethans 2:50

Is this something that is being defined at the grammar level or somewher