Cannot serialize IntlTimeZone objects

[drjayvee]

Description

The following code:

<?php
$tz = IntlTimeZone::createTimeZone('Europe/Amsterdam');
$tz = unserialize(serialize($tz));

var_export($tz->getId());

Resulted in this output:

false

But I expected this output instead:

'Europe/Amsterdam'

It looks like the implementation of __serialize is broken, as the string doesn't contain any object data:

echo serialize(IntlTimeZone::createTimeZone('Europe/Amsterdam'));
// outputs O:12:"IntlTimeZone":0:{}

PHP Version

PHP 7.4.27 (cli) (built: Dec 21 2021 21:31:45) ( NTS )

Operating System

No response

[iluuu1994]

It doesn't look like IntlTimeZone supports serialization.

https://3v4l.org/jnXqP#v8.1.1

$tz = IntlTimeZone::createTimeZone('Europe/Amsterdam');
var_dump(serialize($tz));

string(24) "O:12:"IntlTimeZone":0:{}"

But we could throw an error or at least emit some warning.

[drjayvee]

Would it be difficult to implement serialization? Or do you worry about backwards compatibility?

[iluuu1994]

@drjayvee I know nothing about intl so I'm not sure. Compatibility shouldn't be a concern.

[cmb69]

Would it be difficult to implement serialization?

I don't think it would be difficult, but what is the use case? I assume that IntlTimezone is most often used with IntlCalendar and IntlDateFormatter, but neither of these properly supports (un)serialization. Other classes of the intl extension might exhibit the same behavior.

[drjayvee]

I was under the admittedly naive assumption that every class supports serialization, unless it's especially tricky.

Our particular use case is:

class LocaleConfiguration {
  public IntlTimeZone $timeZone = null;
  public string $locale = 'en-US';
  public int $firstWeekDay = 1;
  // etc
}

And then cache the user's configuration in their session, memory cache, or elsewhere.

The simple yet awkward workaround is

public function __serialize(): array {
  return [
    'timeZone'     => $this->timeZone->getID(),
    'locale'       => $this->locale,
    'firstWeekDay' => $this->firstWeekDay,
    // etc
  ];
}

// reverse for __unserialize()

[cmb69]

Okay, for this case being able to (un)serialize IntlTimeZone objects would make sense.

Note, though, that a lot of internal classes don't support (un)serialization.

[cmb69]

Serialization of these objects will be disallowed as of PHP 8.2.0. PRs to properly support (un)serialization (of individual classes) are welcome!