[PHP-DEV] First time contributor (DateTime::setDate PR)

Mailing Lists php.internals
1

Hi Internals,

I created my first php-src PR yesterday and anticipate I may have to write an RFC for it. I created a wiki account under the handle, “bilge”, and the howto told me to request RFC karma here.

About the PR: I sometimes find it would be useful to only update part of the date. The PR makes all parameters to DateTime(Immutable)::setDate optional in a backwards-compatible manner such that we can elect to update only the day, month, year or any combination of the three (thanks, in part, to named parameters). Without this modification, we must always specify all of the day, month and year parameters to change the date.

To change just one part of the date, StackOverflow users have found various novel ways to work around setDate()'s current limitation, which generally involves calling format() twice, to isolate the specific date parts that should remain constant, and feeding them back into setDate() so they are effectively unchanged. All this leads me to wonder why we can’t just call setDate() with only the parameters we want to change. This is particularly useful when generating a collection of dates that only differ in one aspect (year, day) and/or when working in a templating environment, such as Twig, where doing all the format calls results in multiple statements and logic overhead that we should like to avoid in templating contexts.

Looking forward to hearing your thoughts.

Cheers,
Bilge

2

Hi,

On Sun, 31 Mar 2024, Bilge wrote:

About the PR: I sometimes find it would be useful to only update part of the
date. The PR makes all parameters to DateTime(Immutable)::setDate
<https://www.php.net/manual/en/datetimeimmutable.setdate.php&gt; optional in a
backwards-compatible manner such that we can elect to update only the day,
month, year or any combination of the three (thanks, in part, to named
parameters). Without this modification, we must always specify all of the day,
month and year parameters to change the date.

As I mentioned to you in Room 11, I am not in favour of adhoc API
changes to Date/Time classes. It has now been nearly 18 years since they
were originally introduced, and they indeed could do with an overhaul.

I have been colllecting ideas in

Having different/better modifiers would also be a good thing to talk
about, albeit perhaps on the four mentioned new classes, instead of
adding them to the already existing DateTime and DateTimeImmutable
classes.

In any case, just allowing setDate to be able to just modify the month
is going to introduce confusion, as this will be counter intuitive:

$dt = new DateTimeImmutable("2024-03-31");
$newDt = $dt->setDate( month: 2 );

It is now representing 2024-03-02.

This might be the right answer, but it might also be that the developer
just cared about the month part (and not the day-of-month), in which
case this is a WTF moment.

Picking mofication APIs is not as trivial as it seems, and I would like
to do it *right*.

Feel free to add comments and wishes to the google doc document. In the
near future, I will be writing up an RFC from this.

cheers,
Derick

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3

Hi Derick,

Thanks for your reply!

Indeed, as per your code snippet, this is a WTF moment I had not accounted for and confirm the same result with my patch applied. Generally, my expectation here would be the month must be set to 2, so if the day portion will be invalidated by that change, we should either throw an exception or implicitly coerce it into range, i.e. (new DateTime(“2024-03-31”))->setDate(month: 2); == 2024-02-29. However, I suppose this is not the conversation we’re having as you do not wish to change this API at all, which I respect.

Regarding your brainstorm document, I can’t understand much of it in its current state, and as I am not a subject matter expert, I think you will receive much better feedback from others. In particular, I cannot glean which four classes you are referring to in that document. Yet what I do find interesting is the notion of adding setters to DateTimeImmutable. For my particular use-case—producing a collection of dates incrementing by year in a Twig template—a trivial year setter would do just fine, with the significant caveat that it must implement fluent interface, because I need to call it in an expression context (returning a value), not a statement context (executing a void function separately). Not that Twig cannot execute statements, but it just becomes more verbose, cumbersome and less template-like.

If you were happy for me to add getters and fluent setters for year, I’d be happy to work on that PR, but for month we’re back to the same problem outlined in the opening paragraph (and I suppose the same problem occasionally applies to year, if the day happens to be set to the leap day). Otherwise, I’ll be happy to read over your RFC when it’s ready.

Kind regards, Bilge