Date Timezone unexpected clone, why?

[gzhegow1991]

Description

https://gyazo.com/28d32430a6bcb915755046e4aaca37b9

The following code:

<?php
$tz = new \DateTimeZone('UTC');

$format = 'H:i';

$dt = \DateTime::createFromFormat($format, '15:00', $tz);

var_dump($dt, $tz, $dt->getTimezone());
var_dump($dt->getTimezone() === $tz); // false, what?

Resulted in this output:

false

But I expected this output instead:

true

Once i saw how symfony checks is data was passed to array or gained from default values

It works like
($this->get($key, $default = $this) === $this) // value was default because $this exists only inside class scope

I want to warn programmer that his date is unable to parse timezone, so the date becomes uncomparable.
The case is about "date parser" ensures that "if i passed only time - i mean server timezone and maybe date should be used", but it can be developer mistake that is forget to ask user to sent correct date with his own timezone.

Aproximately it could be compared by timezone name, but when he pass exactly same name expected by format - he's doing all things good, so warning is useless. So the attention point can be, again, aproximately, moved to date format - like "you didnt ask for timezone, you get something unexpected".

Seriosly thought about dates is like floats, you can compare it safely only if you drop parts to same precision, and if you ensure about timezones/dst is correctly parsed. Unable to compare "2nd April" and "2nd April 15:00 BST" because:

1. if you draw both on timeline - it takes different space size as periods (day vs hour, "uncomparable") but... if you make it same size - you can return -1, 0, 1 instead of "intersect left, intersect right, fully included" and so on, so we drop same parts then compare begin points
2. first date has no timezone, so compare them in different time of year gives different result
3. this way i came to requirement to check "what exactly parts of user date was parsed successfully" and "what was default"... Maybe we can safely drop for example microseconds when we compare only by seconds and thats not a problem. But, guess, my feelings joke with me

PHP Version

PHP 8.4.5

Operating System

No response

[DanielEScherzer]

This is because the two timezone objects are different instances, even if they refer to the same timezone:

<?php

$tz = new \DateTimeZone('UTC');
$tz2 = new \DateTimeZone('UTC');
var_dump($tz === $tz2);

also returns false.

[gzhegow1991]

yes, i asked why clone? you compare spl_ids of different objects. i expect same object because this is value object and its value is final (immutabilty is not applicable)

[DanielEScherzer]

Its not a clone, the DateTime class doesn't store the provided timezone object, just the internal details of the object, and then a new object gets created when you call getTimezone

[gzhegow1991]

okey, let name it "its not clone", thats the answer without the answer

[gzhegow1991]

i mean the string format is only way to ensure what parts exactly parsed

the question "what parts of the date is passed by user (parsed from variable)" fully depends of this string "format"

much bigger size of this problem is when parsing date without format (different, dangerous use-case) - parsing "yesterday" automatically set time to "00:00:00", instead "first day of this month" uses "now time"

i tried to implement own order like
function _date_parse(datestring, defaultdate) {}

and i failed because now time is the default, and given word can contain or not contain some parts.

there's internal function date_parse() that returns array with parsed parts of the date, but this array is filled by datestring word too.

I know the user never passes something like "now" or "yesterday" and has to pass a formatted date with timezone every time, otherwise the dates may become incomparable simply because the data is filled with default values ​​with no way to keep them empty to check "was this data sent or received"

so i tried to compare at least parameter that can be passed directly to the function (and may be parsed or the passed at same time) and even there parameter is different. its not parsed, its used from default, that i pass, and even then they different

there's no function date_parse_format(format, formatted) that returns same array as date_parse(datestring)

[iluuu1994]

As @DanielEScherzer has mentioned, this is not a bug. DateTime::getTimezone() constructs a new object, because it doesn't store a PHP timezone object, but rather stores the timezone as a C struct. DateTimeZone specifically implements == comparison for this purpose, the same goes for DateTime. Hence, the right thing to do is to compare using ==, not ===.

What you're asking for is value objects (https://wiki.php.net/rfc/structs-v2), where === checks for value equivalency rather than identity, but this has yet to be accepted.