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Date: Tue, 16 Mar 2021 15:46:58 +0000 (GMT)
To: Moritz Friedrich <m@9dev.de>
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Subject: Re: [PHP-DEV] Add __toString() to DateInterval
From: derick@php.net (Derick Rethans)

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On Tue, 16 Mar 2021, Moritz Friedrich wrote:

> > I also don't understand what you're trying to say. You can't round=20
> > trip every interval as encoded in a DateInterval object through an=20
> > ISO interval string, so we shouldn't attempt to do that.
>=20
> I think you do know what I=E2=80=99m trying to say, but choose to disagre=
e=20
> with me. ISO interval strings allow to express arbitrary intervals of=20
> time as a string, so I don=E2=80=99t know what possible intervals you=E2=
=80=99re=20
> referring to that purportedly cannot be encoded as an interval string.

I already showed you that: "next weekday". It can either be +1 days, +2=20
days, or +3 days.

> If this still revolves around relative intervals, then I don=E2=80=99t se=
e=20
> your point either. The ISO interval specification is the most=20
> appropriate serialization format for time intervals as it is commonly=20
> used and well understood.=20

Maybe, but the DateInterval class does not represent a ISO interval=20
specification, it represents a timelib interval definition, which you=20
can *also* create from an ISO 8601 interval specification.

> By choosing to serialize something like =E2=80=9Enext week=E2=80=9C to an=
 ISO=20
> interval, I=E2=80=99m willingly accepting the conversion to an absolute a=
mount=20
> of time. If the specific start and end dates are relevant for the use=20
> case, an interval is not the appropriate tool, but keeping both dates=20
> is.

That is not what a DateInterval object represents =E2=80=94 instead it=20
represents a definition how to get from one DateTime to another one.
And that can not always be represented by an absolute amount.

> Having a constructor that only accepts an ISO interval but no way to=20
> serialize the duration object back to an interval seems just like an=20
> inconsistent API to me. I=E2=80=99m not particularly attached to using=20
> `__toString()`, something like `toIsoInterval` or similar would do=20
> just as well. The only thing that annoys me here is a one-way parser=20
> for interval specs, deferring the serialization to userland PHP.

Converting to just a simple string is not a serialisation, as it loses=20
information. If you care about serialisation, then you need to come up=20
with a way how to do that for every interval that a DateInterval can=20
represent. PHP's "serialize" can already serialise a DateInterval.

cheers,
Derick

--=20
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