php strtotime +2.5小时的bug？

Question

Having some unexpected behaviour with strtotime:

$d = '2.5';                                   // i.e. hours
$t = '2014-03-20 08:30:00';                   // mysql datetime
$ut = strtotime($t);                          // value: 1395297000
$s = $d * 60 * 60;                            // duration in seconds: 9000
$plusHrs = strtotime($t.' +'.$d.' hours');    // value: 1395315000
$plusSec = strtotime($t.' +'.$s.' seconds');  // value: 1395306000

Expected behaviour would be that $plusHrs = $plusSec. This happens regardless of what date is input, which means it's not a daylight saving issue.

Is this a bug? (PHP v5.3.14)

Answer 1

No, it isn't a bug. strtotime() expects integer values in relative format. Thus, your +2.5 hours would be treated as "+2 GMT" and then "+5" hours and dot would be just ignored. You can change it to comma or even delete as well - result won't change since, again, only integers are parsed. So, such statement will be treated as relative hours addition with respect of GMT offset:

//this is the same things:
//and they mean set timesone to GMT+2 & add 5 hours:
date('Y-m-d H:i:s', strtotime('now +2.5 hours'));
date('Y-m-d H:i:s', strtotime('now +2,5 hours'));
date('Y-m-d H:i:s', strtotime('now +2 5 hours'));

So, for example, +1.5 hours will do add 5 hours for time in GMT +1. That means, end result will depend of current timezone since initial timestamp will be set to current timezone (it's now in sample above).