--TEST-- Test DateInterval::__serialize and DateInterval::__unserialize --FILE-- __serialize()); echo "\n\nCalling __unserialize manually:\n"; $d = new DateInterval('P2Y4DT6H8M'); $d->__unserialize( [ 'from_string' => true, 'date_string' => 'next weekday', ] ); var_dump($d); echo "\n\nUsed serialised interval:\n"; $now = new DateTimeImmutable("2022-04-22 16:25:11 BST"); var_dump($now->add($e)); var_dump($now->sub($e)); ?> --EXPECTF-- Original object: object(DateInterval)#1 (%d) { ["from_string"]=> bool(true) ["date_string"]=> string(%d) "next weekday" } Serialised object: string(%d) "O:12:"DateInterval":2:{s:11:"from_string";b:1;s:11:"date_string";s:%d:"next weekday";}" Unserialised object: object(DateInterval)#2 (2) { ["from_string"]=> bool(true) ["date_string"]=> string(%d) "next weekday" } Calling __serialize manually: array(2) { ["from_string"]=> bool(true) ["date_string"]=> string(%d) "next weekday" } Calling __unserialize manually: object(DateInterval)#3 (2) { ["from_string"]=> bool(true) ["date_string"]=> string(%d) "next weekday" } Used serialised interval: object(DateTimeImmutable)#4 (3) { ["date"]=> string(26) "2022-04-25 16:25:11.000000" ["timezone_type"]=> int(2) ["timezone"]=> string(3) "BST" } Warning: DateTimeImmutable::sub(): Only non-special relative time specifications are supported for subtraction in %s on line %d object(DateTimeImmutable)#4 (3) { ["date"]=> string(26) "2022-04-22 16:25:11.000000" ["timezone_type"]=> int(2) ["timezone"]=> string(3) "BST" }