PHP Internals News: Episode 85: Add IntlDatePatternGenerator

PHP Internals News: Episode 85: Add IntlDatePatternGenerator



Thursday, May 20th 2021, 09:13 BST


London, UK



In this episode of "PHP Internals News" I discuss the Add
IntlDatePatternGenerator RFC with Mel Dafert (GitHub).


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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 85. Today I'm
talking with Mel Dafert about the "Add Intl Date
Pattern Generator RFC" that she's proposing for
inclusion into PHP 8.1. Mel would you please
introduce yourself?
Mel Dafert 0:35

Hello, I am Mel. I've been working professionally
with PHP for about three years. Recently I started
reading the internals mailing list in my free time,
but this is my first time contributing.
Derick Rethans 0:46

What made you think starting to read the PHP
internals mailing list?
Mel Dafert 0:50

I generally like reading mailing lists and issue
trackers. And since I work with PHP, it was
interesting to read what's, what's happening.
Derick Rethans 1:02

That's what I'm trying to read this podcast as well
of course; explaining what happens in the PHP
development. But let's get to your RFC. What is the
problem that you're trying to solve for this?
Mel Dafert 1:14

Currently, PHP exposes the ability for locale
dependent date formatting with the Intl Date
Formatter class. It is basically only three options
for the format: long, medium and short. These options
are not flexible enough in some cases, however. For
example, the most common German format is day dot
numerical month, dot long version of the year.
However, neither the medium nor the short version
provide this, and they use either the long version of
the month, or a short version of the year, neither of
which were acceptable in my situation.
Derick Rethans 1:47

I realize that you basically ran into a problem that
PHP wasn't doing something you wanted to do it. But
what made you actually wanting to contribute this?
Mel Dafert 1:57

I ran into this exact problem at work where I wanted
to format dates in this specific way. After some
research, I found out that ICU, the library that
powers Intl Date Formatter, exposes exactly this
functionality already. It would be relatively easy to
wire this up into PHP and expose it there as well. I
also found in a bug report that other people had this
problem as well, so I decided to try my best at
hacking at the PHP source and make it available to
everyone, using PHP.
Derick Rethans 2:25

Had you ever seen a PHP source code before?
Mel Dafert 2:28

I don't think so. No.
Derick Rethans 2:29

But you are familiar with C a little bit?
Mel Dafert 2:32

On a very basic level, yes.
Derick Rethans 2:34

As part of this RFC What are you trying to suggest to
add to PHP?
Mel Dafert 2:39

ICU exposes a class called date time pattern
generator, which you can pass a locale and so called
skeleton and it generates the correct formatting
pattern for you. Skeleton just includes which part
are supposed to include it, to be included in the
pattern, for example the numerical date, numerical
month, and the long year, and this will generate
exactly the pattern I wanted earlier. It is also a
lot more flexible, for example the skeleton can also
just consist of the month and the year, which was
also not possible so far. I am proposing to add a
Intl Date Pattern Generator class to PHP, which can
be constructed for locale, and exposes the get best
pattern method that generates a pattern from a
skeleton for that locale.
Derick Rethans 3:22

The skeletons, what do you specify in these
skeletons?
Mel Dafert 3:27

It's a similar format to the pattern itself. For
example, it's lowercase y lowercase y uppercase M
uppercase M, would give you only the year and only
the month, if I'm correct, that's exactly what the
skeleton looks like.
Derick Rethans 3:43

But it puts it in the right order?
Mel Dafert 3:45

It puts it in in the right order, and in some cases
also adds extra characters, or even changes the
format slightly, depending on the locale.
Derick Rethans 3:55

So it is a bit of a flexible way to tell the Intl
extension to format them in a slightly more, well how
do you say this, a slightly more intelligent way than
what the standard, long, short and medium constants
do for you.
Mel Dafert 4:11

Exactly.
Derick Rethans 4:12

Why is it so important that you get these formats,
right, or rather I should say, how do these locales
influence formats and why is this important?
Mel Dafert 4:21

There are conventions of how to format dates and
times vary rather strongly between languages and
country. In Austria, for example, nobody would expect
to understand the US format of month slash day last
year. I assume people in England may have the same
issue.
Derick Rethans 4:38

I think everybody has that issue except for people in
the US.
Mel Dafert 4:42

But that only shows the importance of using a format
that people are used to and understand. Other
languages like mainland Chinese even have the words
for day and month included in the format, as far as I
understand. I don't speak Chinese.
Derick Rethans 4:59

Neither do I, but a long time ago when I, when I
added the date time support, not Intl, but PHP
standard date time support, I also looked at locales
that operating systems have. And even these locales,
which is not something that Intl uses now, also
encode these extra characters at least for Japanese,
so that was interesting to see there as well.
Mel Dafert 5:22

There is a lot of sometimes somewhat unexpected
formats.
Derick Rethans 5:27

And I think German sometimes once the add the in
front, and sometimes behind and things like that. I
know there's lots of little intricacies, yes. I see
that he RFC makes an argument about which name to
pick for the new class. Can you elaborate on the two
different options that are?
Mel Dafert 5:44

Yes, this is certainly for us and what I would call
bike shedding. ICU has something of an inconsistency
in its naming. The formatting class is called date
formatter. And the pattern generator class is called
Date Time pattern generator.
Derick Rethans 6:00

So it has the extra word time in it?
Mel Dafert 6:03

Between some inconsistency with Intl Date Formatter,
which already exists in PHP, and the Intl Date Time
pattern generator, or if we make sure PHP is
internally consistent and omit the time in all cases.
So far consensus seems to lean towards the second
option. This is also what the Hack people decided to
use.
Derick Rethans 6:24

And I believe that's the one you are wanting to go
with in this RFCs as well, right?
Mel Dafert 6:28

Exactly. So far, everybody voted slide, or like
express themselves to slightly favour the version
without time. So that's the one I'm going with.
Derick Rethans 6:40

Of course, as you mentioned, this is a fairly small
change to it, but the RFC talks a bit about things to
add in the future, because I believe you weren't
suggesting to add all of these Intl functionality
straightaway. What is this future scope?
Mel Dafert 6:55

ICU would also expose more methods around the
skeletons, for example, turning a pattern back into
its skeleton, or building a list of skeleton and then
mapping to the patterns from scratch. That's what you
would do in theory if you added your own special
locale to this.
Derick Rethans 7:17

I'm not sure how to do that with PHP actually, but I
think ICU allows you to build your own basically
files with settings right?
Mel Dafert 7:25

Exactly. This is omitted all of this, for simplicity,
and because they couldn't think of a use case for it,
personally, at least. If someone does need them, they
could easily be added. It would just be a bunch of
extra methods on the, on the class.
Derick Rethans 7:43

I know that ICU has so much functionality that hasn't
been exposed to PHP, because there's just so much of
it right?
Mel Dafert 7:50

Extremely, yes. I did see that Hack decided to expose
all of them, like all the methods that the class has,
but I really don't see the use of having to document
and test all of these methods when really only one is
going to be used. So I've decided to just go for the
one that I can actually see people using.
Derick Rethans 8:14

And it is always easy to get smaller parts added to
PHP than big things, to begin with.
Mel Dafert 8:21

Exactly.
Derick Rethans 8:22

How has the reception been so far?
Mel Dafert 8:24

I haven't gotten feedback from too many people, but
it seems positive so far. A few people that did give
some feedback were constructive and seem to seem to
like the idea of adding this.
Derick Rethans 8:36

I reckon outside of English speaking countries this
is quite an important thing to actually support,
especially as we just discussed, people are picky
about how these things are formatted.
Mel Dafert 8:46

Very picky.
Derick Rethans 8:48

So the name that you're going for would be Intl Date
Pattern Generator, would it also support patterns for
the time itself?
Mel Dafert 8:55

Of course, just like Intl Date Format also support
formatting time.
Derick Rethans 9:02

It would be strange if it didn't, to be honest.
Mel Dafert 9:04

Yeah.
Derick Rethans 9:05

When do you think you're going to put us up for a
vote for inclusion to PHP 8.1?
Mel Dafert 9:10

I think I sent out the first email about two weeks
ago for opening the discussion. So I was planning to
send out the heads up, either today or tomorrow, and
opening the vote after that.
Derick Rethans 9:23

Okay. To be fair, I think there is very little
controversy in this one, so it would surprise me if
it didn't pass.
Mel Dafert 9:30

That's reassuring. I am somewhat anxious about them.
Derick Rethans 9:33

It's not controversial, it is an, it is perhaps a
niche thing but it is something that is useful, so I
can't see people really be opposing to this. To be
fair, I think it looks like just an omission from
when the Intl extension was written in the first
place.
Mel Dafert 9:48

That's true. It might have not been supported in ICU
at that point.
Derick Rethans 9:54

That is a good point as well because I think the Intl
extension came with PHP five three, or five four,
which I think is now eight years ago or something
like that.
Mel Dafert 10:04

I think, I think ICU might have not had it at the
end. It's an old word, like it's an all supported
versions of PHP.
Derick Rethans 10:13

That is good to know. Would you have anything else to
add?
Mel Dafert 10:16

No, I think that's it.
Derick Rethans 10:17

Thank you for taking the time today to talk to me
about your proposal to add the Intl date pattern
generator to PHP 8.1
Mel Dafert 10:25

Of course. Thank you for having me.
Derick Rethans 10:29

Thank you for listening to this installment of PHP
internals news, a podcast dedicated to demystifying
the development of the PHP language. I maintain a
Patreon account for supporters of this podcast as
well as the Xdebug debugging tool, you can sign up
for Patreon at https://drck.me/patreon. If you have
comments or suggestions, feel free to email them to
derick@phpinternals.news. Thank you for listening and
I'll see you next time.




Show Notes




RFC: Add IntlDatePatternGenerator






Credits



Music: Chipper Doodle v2 — Kevin MacLeod
(incompetech.com) — Creative Commons: By
Attribution 3.0