A Caster is used to convert an object to an array representation that later could be written as a string. All Casters are registered in the AbstractCloner and will automatically be used when we try to clone an object.

There some classes in intl that could benefit from having a caster, see http://php.net/manual/en/book.intl.php

See @nicolas-grekas PR for MessageFormatter as an example: #28551

I think it could be a good idea to have casters for the following classes:

• NumberFormatter
• MessageFormatter
• IntlTimeZone
• IntlDateFormatter
• IntlCalendar
• Locale

Do we need any more?