在PHP 5.3中使用mktime（）中的is_dst（不推荐使用参数）

Question

From 5.3 the is_dst parameter is deprecated in mktime. But I need two previous time in timestamp, one of them with dst and the other without that.

E.g.: first time mktime("03","15","00","08","08","2008",1) and the other mktime("03","15","00","08","08","2008",0)

Can you help me to solve that problem?

Answer 1

Not a full answer, just some ideas I could think of... The DateTime::format() method accepts a format code that tells whether DST is on effect:

$now = new DateTime;
$is_dst = $now->format('I')==1;

Now, in order to know what time it'd be if DST was the other way round, you have to find out when such change happens. This code:

$time_zone = $now->getTimeZone();
var_dump( $time_zone->getTransitions(strtotime('2011-01-01'), strtotime('2011-12-31')) );

... prints:

array(3) {
  [0]=>
  array(5) {
    ["ts"]=>
    int(1293836400)
    ["time"]=>
    string(24) "2010-12-31T23:00:00+0000"
    ["offset"]=>
    int(3600)
    ["isdst"]=>
    bool(false)
    ["abbr"]=>
    string(3) "CET"
  }
  [1]=>
  array(5) {
    ["ts"]=>
    int(1301187600)
    ["time"]=>
    string(24) "2011-03-27T01:00:00+0000"
    ["offset"]=>
    int(7200)
    ["isdst"]=>
    bool(true)
    ["abbr"]=>
    string(4) "CEST"
  }
  [2]=>
  array(5) {
    ["ts"]=>
    int(1319936400)
    ["time"]=>
    string(24) "2011-10-30T01:00:00+0000"
    ["offset"]=>
    int(3600)
    ["isdst"]=>
    bool(false)
    ["abbr"]=>
    string(3) "CET"
  }
}

If you obtain the transitions for year the date belongs to, you can collect a list of offsets according for isdst TRUE and isdst FALSE. Once you pick an appropriate offset, the rest is easy:

$winter_offset = 3600;
$summer_offset = 7200;
$difference = $winter_offset-$summer_offset;
$winter = $now->modify( ($difference<0 ? '' : '+') . $difference . ' seconds');
echo $winter->format('H:i:s');