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. This is Episode 76. In this episode, I’m talking with Nikita Popov about a few more RFCs that he has been working on over the past few months. Nikita, would you please introduce yourself.

Nikita Popov 0:34

Hi, I’m Nikita. I work on PHP core development on behalf of JetBrains.

Derick Rethans 0:39

In the last few PHP releases PHP is handling of types with regards to internal functions and user land functions, has been getting closer and closer, especially with types now. But there’s still one case where type mismatches behave differently between internal and user land functions. What is this outstanding difference?

Nikita Popov 0:59

Since PHP 8.0 on the remaining difference is the handling of now. So PHP 7.0 introduced scalar types for user functions. But scalar types already existed for internal functions at that time. Unfortunately, or maybe like pragmatically, we ended up with slightly different behaviour in both cases. The difference is that user functions, don’t accept null, unless you explicitly allow it using nullable type or using a null default value. So this is the case for all user types, regardless of where or how they occur as parameter types, return values, property types, and independent if it’s an array type or integer type. For internal functions, there is this one exception where if you have a scalar type like Boolean, integer, float, or a string, and you’re not using strict types, then these arguments also accept null values silently right now. So if you have a string argument and you pass null to it, then it will simply be converted into an empty string, or for integers into zero value. At least I assume that the reason why we’re here is that the internal function behaviour existed for a long time, and the use of that behaviour was chosen to be consistent with the general behaviour of other types at the time. If you have an array type, it also doesn’t accept now and just convert it to an empty array or something silly like that. So now we are left with this inconsistency.

Derick Rethans 2:31

Is it also not possible for extensions to check whether null was passed, and then do a different behaviour like picking a default value?

Nikita Popov 2:40

That’s right, but that’s a different case. The one I’m talking about is where you have a type like string, while the one you have in mind is where you effectively have a type like string or null.

Derick Rethans 2:51

Okay.

Nikita Popov 2:52

In that case, of course, accepting null is perfectly fine.

Derick Rethans 2:56

Even though it might actually end up being different defaults.

Nikita Popov 3:01

Yeah. Nowadays we would prefer to instead, actually specify a default value. Instead of using nu

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. This is Episode 75. In this episode, I’m talking with Nikita Popov about a few RFCs that he has been working on over the past few months. Nikita, would you please introduce yourself?

Nikita Popov 0:34

Hi, I’m Nikita, I work at JetBrains on PHP core development and as such I get to occasionally, write PHP proposals RFCs and then talk with Derick about them.

Derick Rethans 0:47

The main idea behind you working on RFCs is that PHP gets new features not, you end up talking to me.

Nikita Popov 0:53

I mean that’s a side benefit,

Derick Rethans 0:55

In any case we have a few to go this time. The first RFC is titled phasing out Serializable, it’s a fairly small RFC. What is it about?

Nikita Popov 1:04

That finishes up a bit of work from PHP 7.4, where we introduced a new serialization mechanism, actually the third one, we have. So we have a bit too many of them, and this removes the most problematic one.

Derick Rethans 1:19

Which three Serializable methods or ways of doing things currently exist?

Nikita Popov 1:24

The first one, which doesn’t really count is just what you get if you don’t do anything, so just all the Object Properties get serialized, and also unserialized, and then we have a number of hooks, you can use to modify that. The first pair is sleep and wake up. Sleep specifies which properties you want to serialize so you can filter out some of them, and wake up allows you to run some code, after unserialization, so you can do some kind of fix up afterwards.

Derick Rethans 1:52

From what I remember, if you use unserialize, where does the wake up the constructor doesn’t get called?

Nikita Popov 1:59

During unserialization the constructor, never gets called.

Derick Rethans 2:03

So wake up a sort of the static factory methods to re rehydrate the objects.

Nikita Popov 2:08

Exactly.

Derick Rethans 2:08

So that’s number one,

Nikita Popov 2:10

Then number two is the Serializable interface, which gives you more control. Namely, you have to actually like return the serialized representation of your object. How it looks like is completely unspecified, you could return whatever you want, though, in practice, what people actually do is to recursively call serialize. And then on the other side when unserializing you usually do the same so you call unserialize on the stream you receive, and then populate your properties based on that. The problem with this mechanism is exactly this recursive serialization call, because it has to share state, with the main serialization. And the

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Derick Rethans 0:14

Hi I’m Derick. Welcome to PHP internals news, the podcast dedicated to explaining the latest developments in the PHP language. This is Episode 74. Today I’m talking with Aaron Piotrowski about a Fiber RFC, that he’s working on together with Nicolas Keller. Aaron, would you please introduce yourself.

Aaron Piotrowski 0:33

Hi everyone I’m Aaron Piotrowski, I started programming with PHP back in 1998 with PHP three, so I’ve just dated myself there but, but I’ve worked with a lot of different languages over the last few decades but PHP is always continually remaining, one of my favourite and I’m always drawn back to it. I’ve gotten a lot more involved with the PHP projects since PHP seven. The Fiber RFC is my first major contribution I have attempted though. In the past I did the RFC for the throwable exception hierarchy. And the Iterable pseudo type in PHP 7.1.

Derick Rethans 1:12

Yeah, these things are both before I started doing the podcast so hence we haven’t spoken yet, at least on here. We’ve actually met at some point in the past. I’ve had a read through the Fiber RFC this morning, but I’m still fairly baffled. Could you perhaps explain in short what Fibers are where the idea comes from. And what’s your specific interest is in adding them to PHP?

Aaron Piotrowski 1:35

A few other languages already have Fibers like Ruby, and they’re sort of similar to threads in that they contain a separate call stack, and a separate memory stack, but they differ from threads in that they exist only within a single process, and that they have to be switched to cooperatively by that process rather than actively by the OS like threads. So sometimes they’re called Green threads, and the generators that are in PHP already are actually somewhat similar to Fibers; but generators differ in that they’re stack less. And so what that means is that generator function can only be interrupted at one layer. Whereas a Fiber can be interrupted anywhere in the call stack. So like it’d be imagine if you had a generator where yield could be very deep in a function call. Rather than at the top level. Like, how generators can be used to make interruptible functions, Fibers can also be used to create similarly interruptible functions, but with again without having to know exactly when it’s going to be interrupted not at the top level but at any point in the call stack. And so the main motivation behind wanting to add this feature is to make asynchronous programming in PHP much easier and eliminate the distinction that usually exists between async code that has used promises and synchronous code that we’re all used to.

Derick Rethans 3:09

So what specifically are you proposing to ask to PHP here then?

Aaron Piotrowski 3:12

Specifically I’m looking at adding a low level Fiber API, that’s really aimed specifically at async framework authors to create their own more opinionated API’s on top of that low level API. So adds just a couple of classes: Fiber, and a FiberScheduler on within a couple of exception classes and reflection classes for inspecting Fibers. When a Fiber is suspended to the execution switch is to FiberScheduler, which is then a special Fiber, that’s able to start and resume, regular user Fibers. So a Fiber scheduler is general