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Date: Fri, 11 Sep 2015 09:51:18 +0100 (BST)
To: Yasuo Ohgaki <yohgaki@ohgaki.net>
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Subject: Re: Invalid date/time handling - strtotime()
From: derick@php.net (Derick Rethans)

On Wed, 9 Sep 2015, Yasuo Ohgaki wrote:

> Hi Derick,
> 
> On Wed, Sep 9, 2015 at 1:31 AM, Derick Rethans <derick@php.net> wrote:
> > Currently, it works as follows by design:
> >
> > - the parser, allows for each unit (year, month, day, hour, minute,
> >   second) the full range of values. For a year that's just 4 digits, for
> >   a month that's 0-12, day is 0-31 and for hour and minute it's 0-59.
> >
> > - 60 is allowed for seconds, as sometimes date strings with that
> >   leapsecond do show up. But PHP implements Unix time where "60" is not
> >   a valid second number and hence it overflows. There is some more
> >   background information at http://drck.me/leapsec-6ye
> >
> > - strtotime() returns false if any number is outside of the ranges, and
> >   new DateTime() throws an exception.
> >
> > - the parser is dumb, and doesn't do any checks to make it faster (and
> >   more generic)
> >
> > - *but*, there is an additional check if you pass in an invalid date
> >   (like your suggested $strict):
> >
> >   $ php -r '$res = date_parse("2015-09-31"); var_dump($res["warnings"]);'
> >
> >   array(1) {
> >     [11] =>
> >     string(27) "The parsed date was invalid"
> >   }
> >
> > - It is already possible to handle the edge cases, but then you need to
> >   supply the right format. Otherwise there are too many possible
> >   confusing and unintuitive results coming out of the parser:
> >
> >   php -r '$res = date_create_from_format("Y-m-d", "2015-09-34"); var_dump($res);'
> >
> >   class DateTime#1 (3) {
> >     public $date =>
> >     string(26) "2015-10-04 17:24:43.000000"
> >     public $timezone_type =>
> >     int(3)
> >     public $timezone =>
> >     string(13) "Europe/London"
> >   }
> >
> > - We can't add a second argument to strtotime(), because it already
> >   exists.
> >
> > - Having a "strict" option to strtotime() does also not work, as that
> >   would mean two distinct parsing routines.
> >
> > With all those concerns, as well as functionality to handle edge cases
> > in place, I do not think we should change anything.
> 
> Thank you for detailed explanation.
> I'm OK with current design/API. How about add documentation for more precise
> date/time parsing and handling to strtotime() manual page?

There is a whole section at:

http://docs.php.net/manual/en/datetime.formats.php 

Although it doesn't seem to get the 60 for seconds right. 

> I made a bug report to track this.
> https://bugs.php.net/bug.php?id=70463

Ok, cool.

cheers,
Derick