Introduction to the constants of the new date function in PHP 5_PHP Tutorial

The following constants have been defined since PHP 5.1.1 to provide standard date expression methods, which can be used in date format functions (such as date()).

DATE_ATOM(string)

Atomic clock format (such as: 2005-08-15T15:52:01+00:00)

DATE_COOKIE(string)

HTTP Cookies format (eg: Mon, 15 Aug 2005 15:52:01 UTC)

DATE_ISO8601(string)

ISO-8601 (eg: 2005-08-15T15:52:01 +0000)

DATE_RFC822(string)

RFC 822 (eg: Mon, 15 Aug 2005 15:52:01 UTC)

DATE_RFC850(string)

RFC 850 (eg: Monday, 15-Aug-05 15:52:01 UTC)

DATE_RFC1036(string)

RFC 1036 (eg: Monday, 15-Aug-05 15 :52:01 UTC)

DATE_RFC1123(string)

RFC 1123 (such as: Mon, 15 Aug 2005 15:52:01 UTC)

DATE_RFC2822(string)

RFC 2822 (eg: Mon, 15 Aug 2005 15:52:01 +0000)

DATE_RSS(string)

RSS (eg: Mon, 15 Aug 2005 15: 52:01 UTC)

DATE_W3C(string)

World Wide Web Consortium (such as: 2005-08-15T15:52:01+00:00)

For example, To output the date format required by RSS, you can simply use the following code:

echo date(DATE_RSS);