The DateTimeInterface interface

(PHP 5 >= 5.5.0, PHP 7, PHP 8)

DateTimeInterface was created so that parameter, return, or property type declarations may accept either DateTimeImmutable or DateTime as a value. It is not possible to implement this interface with userland classes.

Common constants that allow for formatting DateTimeImmutable or DateTime objects through DateTimeImmutable::format() and DateTime::format() are also defined on this interface.

interface DateTimeInterface {

/* Constants */

public const string ATOM = "Y-m-d\\TH:i:sP";

public const string COOKIE = "l, d-M-Y H:i:s T";

public const string ISO8601 = "Y-m-d\\TH:i:sO";

public const string ISO8601_EXPANDED = "X-m-d\\TH:i:sP";

public const string RFC822 = "D, d M y H:i:s O";

public const string RFC850 = "l, d-M-y H:i:s T";

public const string RFC1036 = "D, d M y H:i:s O";

public const string RFC1123 = "D, d M Y H:i:s O";

public const string RFC7231 = "D, d M Y H:i:s \\G\\M\\T";

public const string RFC2822 = "D, d M Y H:i:s O";

public const string RFC3339 = "Y-m-d\\TH:i:sP";

public const string RFC3339_EXTENDED = "Y-m-d\\TH:i:s.vP";

public const string RSS = "D, d M Y H:i:s O";

public const string W3C = "Y-m-d\\TH:i:sP";

/* Methods */

public function diff(DateTimeInterface $targetObject, bool $absolute = false): DateInterval

public function format(string $format): string

public function getMicrosecond(): int

public function getOffset(): int

public function getTimestamp(): int

public function getTimezone(): DateTimeZone|false

public function __serialize(): array

public function __unserialize(array $data): void

#[\Deprecated(
since: '8.5',
message: 'this method is obsolete, as serialization hooks are provided by __unserialize() and __serialize()',
)]
public function __wakeup(): void

}

DateTimeInterface::ATOM string
DATE_ATOM: Atom (example: 2005-08-15T15:52:01+00:00); compatible with ISO-8601, RFC 3339, and XML Schema
DateTimeInterface::COOKIE string
DATE_COOKIE: HTTP Cookies (example: Monday, 15-Aug-2005 15:52:01 UTC)
DateTimeInterface::ISO8601 string
DATE_ISO8601: ISO-8601-like (example: 2005-08-15T15:52:01+0000)

Note:
This format is not compatible with ISO-8601, but is left this way for backward compatibility reasons. Use DateTimeInterface::ISO8601_EXPANDED, DateTimeInterface::ATOM for compatibility with ISO-8601 instead. (ref ISO8601:2004 section 4.3.3 clause d)
DateTimeInterface::ISO8601_EXPANDED string
DATE_ISO8601_EXPANDED: ISO-8601 Expanded (example: +10191-07-26T08:59:52+01:00)

Note:
This format allows for year ranges outside of ISO-8601's normal range of 0000-9999 by always including a sign character. It also ensures that the timezone part (+01:00) is compatible with ISO-8601.
DateTimeInterface::RFC822 string
DATE_RFC822: RFC 822 (example: Mon, 15 Aug 05 15:52:01 +0000)
DateTimeInterface::RFC850 string
DATE_RFC850: RFC 850 (example: Monday, 15-Aug-05 15:52:01 UTC)
DateTimeInterface::RFC1036 string
DATE_RFC1036: RFC 1036 (example: Mon, 15 Aug 05 15:52:01 +0000)
DateTimeInterface::RFC1123 string
DATE_RFC1123: RFC 1123 (example: Mon, 15 Aug 2005 15:52:01 +0000)
DateTimeInterface::RFC7231 string
DATE_RFC7231: RFC 7231 (since PHP 7.0.19 and 7.1.5) (example: Sat, 30 Apr 2016 17:52:13 GMT)
DateTimeInterface::RFC2822 string
DATE_RFC2822: RFC 2822 (example: Mon, 15 Aug 2005 15:52:01 +0000)
DateTimeInterface::RFC3339 string
DATE_RFC3339: Same as DATE_ATOM
DateTimeInterface::RFC3339_EXTENDED string
DATE_RFC3339_EXTENDED: RFC 3339 EXTENDED format (example: 2005-08-15T15:52:01.000+00:00)
DateTimeInterface::RSS string
DATE_RSS: RSS (example: Mon, 15 Aug 2005 15:52:01 +0000)
DateTimeInterface::W3C string
DATE_W3C: World Wide Web Consortium (example: 2005-08-15T15:52:01+00:00)

Version	Description
8.5.0	The `DATE_RFC7231` and `DateTimeInterface::RFC7231` constants have been deprecated.
8.4.0	The class constants are now typed.
8.2.0	The constant `DateTimeInterface::ISO8601_EXPANDED` was added.
7.2.0	The class constants of DateTime are now defined on DateTimeInterface.

DateTimeInterface::diff — Returns the difference between two DateTime objects
DateTimeInterface::format — Returns date formatted according to given format
DateTimeInterface::getMicrosecond — Gets the microsecond part of the Unix timestamp
DateTimeInterface::getOffset — Returns the timezone offset
DateTimeInterface::getTimestamp — Gets the Unix timestamp
DateTimeInterface::getTimezone — Return time zone relative to given DateTime
DateTime::__serialize — Serialize a DateTime
DateTime::__unserialize — Unserialize an Datetime
DateTime::__wakeup — The __wakeup handler

The DateTimeInterface interface

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