php DateTimeZone->getOffset() returns invalid offset for GMT timezones

Hopefully someone notices what is the cause for the problem I'm having.

For all other timezones such as "Europe/Helsinki" the offs开发者_开发知识库et calculation below returns correct values, but for some reason I get negative value for 'Etc/GMT+2' style timezones and vice versa (e.g. for Etc/GMT-2 I get positive value, 7200).

$dateTimeZone = new DateTimeZone('Etc/GMT+2');
echo $dateTimeZone->getOffset(new DateTime("now", new DateTimezone( 'UTC' )));

Expected: 7200 Result: -7200

The Etc/GMT+2 timezone is what would otherwise be called "GMT -2" or represented like <date time>-02:00.

This is due to the way that POSIX represents those types of timezone offsets:

The offset specifies the time value you must add to the local time to get a Coordinated Universal Time value. It has syntax like [+|-]hh[:mm[:ss]]. This is positive if the local time zone is west of the Prime Meridian and negative if it is east. The hour must be between 0 and 23, and the minute and seconds between 0 and 59.

^{From TZ Variable.}

And:

Numeric time zone abbreviations typically count hours east of UTC, e.g., +09 for Japan and -10 for Hawaii. However, the POSIX TZ environment variable uses the opposite convention. For example, one might use TZ="JST-9" and TZ="HST10" for Japan and Hawaii, respectively. If the tz database is available, it is usually better to use settings like TZ="Asia/Tokyo" and TZ="Pacific/Honolulu" instead, as this should avoid confusion, handle old time stamps better, and insulate you better from any future changes to the rules. One should never set POSIX TZ to a value like "GMT-9", though, since this would falsely claim that local time is nine hours ahead of UTC and the time zone is called "GMT".

^{From Sources for Time Zone and Daylight Saving Time Data - Time notation.}

From http://www.php.net/manual/en/timezones.others.php#64310

The plus and minus signs (+/-) are not intuitive. For example,

"Etc/GMT-10" actually refers to the timezone "(GMT+10:00) Canberra,Sydney,Melbourne".