Re: [PHP-I18N] What's the scope of putenv()?

Karen Andrien wrote:
> Hi there,
> 
> I'm researching how to implement timezones in PHP, and found a wealth
> of information on the subject.  For Linux users, it all seems to boil
> down to one recommendation:  use the putenv("TZ=xxx") statement.
> 
> The software I'm working on needs to be able to display a grid of hours
> for the current date, for a user in any timezone.  (The timezone can be
> passed to the script as, e.g., $_COOKIE['TZ'] = 'America/Vancouver'.) 
> So far so good.  putenv() will change the timezone environment variable
> and the operating system will take care of the rest transparently.
> 
> However, I haven't been able to find any information on the scope of
> the putenv() statement.  What happens if users from Vancouver and
> Toronto log on at the same time?
> 
> The PHP documentation says putenv() applies "for the current request"
> only, but several users on the documentation page disagree.  They claim
> that putenv() has changed the time zone for both the current request
> and other future requests at random.
> 
> Can anybody clarify the putenv() scope for me?
> 
> My best guess is that the scope is PHP request-level, but Apache
> session-level.  When putenv() is called, it applies to the current
> Apache session, and all future connections which happen to arrive on
> the same connection.  If this is true, I would simply have to restore
> putenv() to the default at the end of the script.

seems like a more than reasonable assessment. regardless of what it is
supposed to do there apparently seems to be problems for some people,
sometimes on some kinds of systems - given that fact you would be best off
restoring the ENV to the original state at the end of each script
(you might consider an auto_append_file directive to take care of such stuff.)

> 
> But I don't want to test this on my system in case I'm wrong.  I don't
> have a separate development machine.

nothing a quick 'apachectl graceful' won't fix :-)

> 
> Here are all the possibilities I've thought of:
>    * Current PHP request only
>    * Current PHP session only (including future requests)
>    * Current PHP process only (including random future requests)

this would seemingly point to the ENV var being set for the given apache
children process - every request is handled by an arbitrary child process
and there will be a number of them hanging around waiting to handle a
request at any given time (dependent on your apache conf.) and a child process
is usually set up to handle a given number of reuqest before being killed
off - that would more than account for the 'random' part.

>    * All of PHP (including other current requests)
> 
>    * Current Apache request only
>    * Current Apache connection only (including random future requests)
>    * All of Apache (including other current connections)
> 
>    * All of Linux (this is such a bad idea that I'm sure it's wrong)
> 
> Thanks very much,
> Karen Andrien
> 
> 
> __________________________________________________
> Do You Yahoo!?
> Tired of spam?  Yahoo! Mail has the best spam protection around 
> http://mail.yahoo.com 
>