datetime - PHP 5.4 Can't Determine Time Zones on its own

Question

I'm just looking for a little clarification on this. PHP 5.4 eliminated the TZ environmental variable and the "guessing" that date_default_timezone_get used to do. So now it appears to me there's no way to get the server's timezone at all.

So my question is this: is it possible to get the server timezone in PHP 5.4? I know I can manually set it in php.ini, but that seems kind of silly when there's a computer that's perfectly capable of knowing what time it is. I expect the answer is "no", so perhaps somebody can shed some light on why a programming language would be unable to determine its time zone if that's the case.

Answer 1

There is no reliable way to guess timezone on every system. Different systems use different conventions and sometimes even different timezone definitions (such as Unix and Windows), sometimes have conflicting timezone specifiers (the same 3-letter zone abbreviation can mean different things in different places). So if you want to have code that is portable between systems, the only way to reliably do it is to ask the user. See for example this thread: http://marc.info/?t=132356551500002&r=1&w=2 on some of the issues with it (look for emails from Derick Rethans - he is the PHP datetime extension maintainer).

If you have a way to find out timezone that you trust - such as TZ variable - then you could always do date_default_timezone_set($_SERVER['TZ']);. However in general this is not a reliable method, so it must be your decision to trust it, PHP can not make it for you.