Doc #54516 [Opn]: DateTime Object does not always update using DateTime::add method

Edit report at http://bugs.php.net/bug.php?id=54516&edit=1 ID: 54516 Updated by: salathe@php.net Reported by: theanomaly dot is at gmail dot com Summary: DateTime Object does not always update using DateTime::add method Status: Open Type: Documentation Problem Package: Date/time related Operating System: Linux PHP Version: 5.3.6 -Assigned To: +Assigned To: derick Block user comment: N Private report: N New Comment: Simpler reproduce case: <?php $date = new DateTime('first day of this month'); // Displays unexpected behaviour -- string(10) "2011-04-01" $test = clone $date; var_dump($test->add(new DateInterval('P1W'))->format('Y-m-d')); // Displays expected behaviour -- string(10) "2011-04-08" $test = clone $date; var_dump($test->modify('+1 week')->format('Y-m-d')); ?> Assigning to Derick to determine whether we simply document this behaviour, or it gets changed. Previous Comments: ------------------------------------------------------------------------ [2011-04-13 03:32:25] theanomaly dot is at gmail dot com I tried adding a new patch to better explain why using a relative time format in the DateTime object constructor will not result in the desired effect when attempting to add a DateInterval with DateTime::add, but the patch failed - it is saved in the PHP Docbook Online Editor, however under /en/reference/datetime/book.xml with the appropriate amendment to the examples. I hope this helps others as the documentation is not clear about this bit. ------------------------------------------------------------------------ [2011-04-12 20:33:10] theanomaly dot is at gmail dot com Description: ------------ The DateTime class does not seem to update the object properly, specifically when the 'time' specified in the constructor of the object is relative time format (such as first day of this month). The test case is reproducible on PHP 5.3.6 as well as PHP 5.3.2 using the test script I've included below. A DateTime::diff after using a DateTime::add method on the object results in 0 for all periods (when the period specified with DateInterval is in Days). This clearly is not the expected behavior as using PT24H will increase the object date by one day, but not result in objects date being updated, while P1D (or P1W - which translates to days) will have no effect at all. Test script: --------------- $timezone = new DateTimeZone(date_default_timezone_get()); $times['relative1'] = new DateTime('first day of this month', $timezone); $times['relative2'] = new DateTime('-1 week', $timezone); $times['fixed'] = new DateTime('4/1/2011 12:00:00 AM', $timezone); $intervals['PT24H'] = new DateInterval('PT24H'); $intervals['P1D'] = new DateInterval('P1D'); $intervals['P1W'] = new DateInterval('P1W'); $intervals['P1M'] = new DateInterval('P1M'); $intervals['P1Y'] = new DateInterval('P1Y'); echo "<pre>"; foreach ($times as $type => $time) { foreach ($intervals as $period => $interval) { $str = "From " . $time->format('m/d/Y H:i:s') . " To "; $last_time = new DateTime($time->format('m/d/Y H:i:s')); $time->add($interval); $str .= $time->format('m/d/Y h:i:s') . " - PERIOD: $period"; echo "<b>Using <i>$type</i> $str</b>\r\n"; echo $time->diff($last_time)->format('%y years, %m months, %d days, %h hours, %i minutes, %s seconds.') . '<br />'; } } echo "</pre>"; Expected result: ---------------- Specify a DateTime object using relative time format of 'first day of this month' DateTime object updates by 1 day when using DateTime::add() with a DateInterval('P1D') on that object. Actual result: -------------- DateTime object does not update even though the DateInterval is valid and works on other DateTime objects of different, or non-relative, time. ------------------------------------------------------------------------ -- Edit this bug report at http://bugs.php.net/bug.php?id=54516&edit=1