Add __toString() to DateInterval

Le 03/03/2021 à 11:37, Moritz Friedrich a écrit :

Hi internals,
I’ve been active in the PHP ecosystem as @Radiergummi for quite a while now, but not on internals yet, so: nice to meet you all!

I would like to propose adding a __toString() method to the DateInterval class that should return a valid ISO8601 interval (https://en.wikipedia.org/wiki/ISO_8601#Time_intervals). As it stands, the class supports creating instances from such interval strings passed to its constructor, but the reverse isn’t true: The only way to build a string representation of the interval is by querying the DateInterval::format method for the individual durations multiple times (see https://stackoverflow.com/questions/33787039/format-dateinterval-as-iso8601#answers for examples).

Allowing to cast DateIntervals to strings would make the most sense in my opinion, and probably doesn’t break BC. Use cases include communicating with other APIs that work with ISO8601, or persistence of periods in databases, for example.

So instead of the following:

 function formatDateInterval(DateInterval $interval, string $default = 'PT0S'): string {
     return rtrim(str_replace(
         ['M0S', 'H0M', 'DT0H', 'M0D', 'P0Y', 'Y0M', 'P0M'],
         ['M', 'H', 'DT', 'M', 'P', 'Y', 'P'],
         $interval->format('P%yY%mM%dDT%hH%iM%sS')
     ), 'PT') ?: $default;
 }
 
 formatDateInterval(new DateInterval('P1DT5H')) === 'P1DT5H'

I’d like to be able to do this:

 (string)new DateInterval('P1DT5H') === 'P1DT5H'

Following alternative approaches come to mind:

1. Adding a new, specialized method to the class (eg. DateInterval::toIsoString(): string):
   While being the most BC-safe option, this would be completely different to the rest of the PHP date APIs.

2. Adding a new interval format constant to be passed to DateInterval::format (eg. DATE_INTERVAL_ISO8601):
   Most in line with the DateTime API, but probably requires special case handling in format code.

From those, having __toString seems most desirable to me.
While I’m not proficient with C, I’d really like to see this implemented and would gladly help out where I can. Might someone be able to advise?

Sincerely
Moritz / Radiergummi

Hello,

I don't like implicit __toString() methods, they have to be very
carefully documented and it's "magic". Wouldn't it be best to have both
the toIsoString() and __toString() (as a fallback) methods ?

Having the constant is a good idea too, it would make it probably more
consistent with the DateTime class, I'm not opposed having three
variations to do skin the same cat.

Regards,

Pierre

Hi internals,
I’ve been active in the PHP ecosystem as @Radiergummi for quite a while
now, but not on internals yet, so: nice to meet you all!

I would like to propose adding a __toString() method to the
DateInterval class that should return a valid ISO8601 interval
(https://en.wikipedia.org/wiki/ISO_8601#Time_intervals). As it stands,
the class supports creating instances from such interval strings passed
to its constructor, but the reverse isn’t true: The only way to build a
string representation of the interval is by querying the
DateInterval::format method for the individual durations multiple
times (see
https://stackoverflow.com/questions/33787039/format-dateinterval-as-iso8601#answers for examples).

Allowing to cast DateIntervals to strings would make the most sense
in my opinion, and probably doesn’t break BC. Use cases include
communicating with other APIs that work with ISO8601, or persistence of
periods in databases, for example.

So instead of the following:

function formatDateInterval(DateInterval $interval, string $default 

= 'PT0S'): string {
return rtrim(str_replace(
['M0S', 'H0M', 'DT0H', 'M0D', 'P0Y', 'Y0M', 'P0M'],
['M', 'H', 'DT', 'M', 'P', 'Y', 'P'],
$interval->format('P%yY%mM%dDT%hH%iM%sS')
), 'PT') ?: $default;
}

formatDateInterval(new DateInterval('P1DT5H')) === 'P1DT5H'

I’d like to be able to do this:

(string)new DateInterval('P1DT5H') === 'P1DT5H'

Following alternative approaches come to mind:

1. Adding a new, specialized method to the class (eg.
   DateInterval::toIsoString(): string):
   While being the most BC-safe option, this would be completely
   different to the rest of the PHP date APIs.

2. Adding a new interval format constant to be passed to
   DateInterval::format (eg. DATE_INTERVAL_ISO8601):
   Most in line with the DateTime API, but probably requires special
   case handling in format code.

From those, having __toString seems most desirable to me.
While I’m not proficient with C, I’d really like to see this
implemented and would gladly help out where I can. Might someone be
able to advise?

I agree that easier round-tripping of interval data is a good thing. As for which approach to take, I think we should defer to Derick, or at least see what his input is. :-) I don't have a super strong preference between these 3 options, other than not liking the idea of tossing that off to user space. For better or worse DateTime is a core functionality and API, so it should be implemented in one place. Beyond that, whatever Derick feels is most consistent with the rest of the API is OK by me.

Let's not bikeshed this into a larger overhaul of the whole DateTime API. :-)

--Larry Garfield

I would like to propose adding a __toString() method to the
DateInterval class that should return a valid ISO8601 interval
(https://en.wikipedia.org/wiki/ISO_8601#Time_intervals). As it stands,
the class supports creating instances from such interval strings
passed to its constructor, but the reverse isn’t true: The only way to
build a string representation of the interval is by querying the
DateInterval::format method for the individual durations multiple
times (see
https://stackoverflow.com/questions/33787039/format-dateinterval-as-iso8601#answers
for examples).

The DateInterval class can also contain intervals that can't be
represented with such an ISO string. For example, how are you going to
do:

$dt = DateInterval::createFromDateString( "next weekday" );

or

$dt = DateInterval::createFromDateString( 'next Monday 02:00' );

__toString needs to work in every case, and I don't think you can do
that with ISO 8601 interval strings.

cheers,
Derick

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