The DateTimeInterface interface

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

Introduction

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 synopsis

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]
public function __wakeup(): void
}

Predefined Constants

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)

Changelog

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.

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