Since PHP 7.1 behavior of this constructor without arguments have changed.
From now on microseconds are filled with actual value. In versions <=7.0 microseconds ware set to '000000'
(PHP 5 >= 5.2.0, PHP 7)
DateTime::__construct -- date_create — Returns new DateTime object
面向对象风格
过程化风格
Returns new DateTime object.
time日期/时间字符串。正确格式的说明详见 日期与时间格式。
Enter "now" here to obtain the current time when using
the $timezone parameter.
timezone
A DateTimeZone object representing the
timezone of $time.
If $timezone is omitted,
the current timezone will be used.
Note:
The
$timezoneparameter and the current timezone are ignored when the$timeparameter either is a UNIX timestamp (e.g. @946684800) or specifies a timezone (e.g. 2010-01-28T15:00:00+02:00).
Returns a new DateTime instance.
过程化风格在失败时返回 FALSE。
Emits Exception in case of an error.
| 版本 | 说明 |
|---|---|
| 5.3.0 |
If time contains an invalid
date/time format, then an
exception is now thrown. Previously an error was emitted.
|
| 7.1 | From now on microseconds are filled with actual value. Not with '00000'. |
Example #1 DateTime::__construct() example
面向对象风格
<?php
try {
$date = new DateTime('2000-01-01');
} catch (Exception $e) {
echo $e->getMessage();
exit(1);
}
echo $date->format('Y-m-d');
?>
过程化风格
<?php
$date = date_create('2000-01-01');
if (!$date) {
$e = date_get_last_errors();
foreach ($e['errors'] as $error) {
echo "$error\n";
}
exit(1);
}
echo date_format($date, 'Y-m-d');
?>
以上例程会输出：
2000-01-01
Example #2 Intricacies of DateTime::__construct()
<?php
// Specified date/time in your computer's time zone.
$date = new DateTime('2000-01-01');
echo $date->format('Y-m-d H:i:sP') . "\n";
// Specified date/time in the specified time zone.
$date = new DateTime('2000-01-01', new DateTimeZone('Pacific/Nauru'));
echo $date->format('Y-m-d H:i:sP') . "\n";
// Current date/time in your computer's time zone.
$date = new DateTime();
echo $date->format('Y-m-d H:i:sP') . "\n";
// Current date/time in the specified time zone.
$date = new DateTime(null, new DateTimeZone('Pacific/Nauru'));
echo $date->format('Y-m-d H:i:sP') . "\n";
// Using a UNIX timestamp. Notice the result is in the UTC time zone.
$date = new DateTime('@946684800');
echo $date->format('Y-m-d H:i:sP') . "\n";
// Non-existent values roll over.
$date = new DateTime('2000-02-30');
echo $date->format('Y-m-d H:i:sP') . "\n";
?>
以上例程的输出类似于：
2000-01-01 00:00:00-05:00 2000-01-01 00:00:00+12:00 2010-04-24 10:24:16-04:00 2010-04-25 02:24:16+12:00 2000-01-01 00:00:00+00:00 2000-03-01 00:00:00-05:00
Since PHP 7.1 behavior of this constructor without arguments have changed.
From now on microseconds are filled with actual value. In versions <=7.0 microseconds ware set to '000000'
I'm surprised this hasn't been mentioned, but when constructing a DateTime with just the year as a string, DateTime will pre-initialize itself with NOW and then replace the year, so if today is 7/12/2016:
<?php
print((new DateTime('2015'))->modify('+1 day')->format('Y-m-d'));
?>
results in 2016-07-13
This seems to work as expected, at least now:
<?php
$timezone1 = new \DateTimeZone('Europe/Sofia');
$timezone2 = new \DateTimeZone('UTC');
$sometime1 = '2014-03-30 02:59:59';
$sometime2 = '2014-03-30 03:00:00';
$date1 = new \DateTime($sometime1, $timezone1);
$date2 = new \DateTime($sometime2, $timezone1);
echo $date1->format('D M j, Y G:i:s T') . '<br>';
echo $date2->format('D M j, Y G:i:s T') . '<br>';
$date1->setTimezone($timezone1);
$date2->setTimezone($timezone1);
echo $date1->format('D M j, Y G:i:s T') . '<br>';
echo $date2->format('D M j, Y G:i:s T') . '<br>';
$date1->setTimezone($timezone2);
$date2->setTimezone($timezone2);
echo $date1->format('D M j, Y G:i:s T') . '<br>';
echo $date2->format('D M j, Y G:i:s T') . '<br>';
This outputs:
Sun Mar 30, 2014 2:59:59 EET
Sun Mar 30, 2014 4:00:00 EEST
Sun Mar 30, 2014 2:59:59 EET
Sun Mar 30, 2014 4:00:00 EEST
Sun Mar 30, 2014 0:59:59 UTC
Sun Mar 30, 2014 1:00:00 UTC
When passing a non US or SQL date string the date will be formatted incorrectly.
// UK date d/m/Y.
$date_time = "08/03/2016 00:00:00";
$dt = new DateTime($date_time, new DateTimeZone("Europe/London"));
// Gives 2016-08-03
echo $dt->format("Y-m-d");
Impossible times due to daylight savings are handled by this function in a way similar to impossible dates, with the difference that this is not an error (i.e. a consequent call to DateTime::getLastError() yields nothing).
For example:
In the timezone "Europe/Berlin" on Sunday, March 30 2014 there was no 02:30 am, because that our is being skipped due to daylight savings on that day.
<?php
$tz = new DateTimeZone("Europe/Berlin");
$impossible_time = "2014-03-30T02:30:00";
$date = new DateTime($impossible_time, $tz);
var_dump($date->getLastErrors());
echo "The impossible time '$impossible_time' is interpreted as: " . $date->format(DateTime::ISO8601) . "\n";
/*
Yields:
array(4) {
'warning_count' =>
int(0)
'warnings' =>
array(0) {
}
'error_count' =>
int(0)
'errors' =>
array(0) {
}
}
The impossible time '2014-03-30T02:30:00' is interpreted as: 2014-03-30T03:30:00+0200
*/
?>
That is similar to how, for example, Febuary 29, 2014 would be handled, which would be interpreted as March 1, 2014. The difference is, that with the date that would be an error, with the time it is not.
Ambigous times due to daylight savings are handled as the second possibility. For example the time 2:30 am occurred twice on October 26, 2014 in the timezone "Europe/Berlin".
<?php
$tz = new DateTimeZone("Europe/Berlin");
$ambiguous_time = "2014-10-26T02:30:00";
$date = new DateTime($ambiguous_time, $tz);
echo "The ambiguous time '$ambiguous_time' is interpreted as: " . $date->format(DateTime::ISO8601) . "\n";
/*
Yields:
The ambiguous time '2014-10-26T02:30:00' is interpreted as: 2014-10-26T02:30:00+0100
*/
?>
Note that "2014-10-26T02:30:00+0200", one hour earlier, would be a correct answer as well.
It is worth noting:
If you have not setup a default timezone, an Exception (or error if PHP < 5.3.0) will be thrown even when the $time parameter of the constructor includes a timezone or is a UNIX timestamp.
At least for me, this was unexpected considering that the $timezone parameter is ignored in the cases when "the $time parameter either is a UNIX timestamp (e.g. @946684800) or specifies a timezone (e.g. 2010-01-28T15:00:00+02:00)."
If time cannot be parsed an exception of type Exception is thrown which can be caught, however an E_WARNING is emitted as well. This might be confusing if you are converting warnings to exceptions in your error or shutdown handler.
<?php
try {
$var = new DateTime('some invalid date format');
}
catch (Exception $ex) {}
$warning = error_get_last(); // will contain warning info
?>
Note that the DateTime ctor also accepts boolean false and empty strings, and treats them the same as NULL (i.e. result is current date and time). This may lead to unexpected results if you forward function return values without explicitly checking them first.
Empty arrays and boolean true trigger PHP warnings OTOH.
(checked with PHP 5.5.18)
Be careful working with MySQL dates representing point of transition to Daylight Saving Time.
The constructor of DateTime will convert timezone abbreviation to DST but not the time.
<?php
$timeZone = new DateTimeZone('Europe/Sofia');
$transitionToDst = '2014-03-30 03:00:00';
$date = new DateTime($transitionToDst, $timeZone);
// Outputs: Sun Mar 30, 2014 3:00:00 EEST
// Correct: Sun Mar 30, 2014 4:00:00 EEST
echo $date->format('D M j, Y G:i:s T') . '<br>';
// Explicitly setting timezone or adding one second fixes this
$cloneForAdding = clone $date;
$date->setTimezone($timeZone);
// Outputs: Sun Mar 30, 2014 4:00:00 EEST
echo $date->format('D M j, Y G:i:s T') . '<br>';
$cloneForAdding->add(new DateInterval('PT1S'));
// Outputs: Sun Mar 30, 2014 4:00:01 EEST
echo $cloneForAdding->format('D M j, Y G:i:s T');
?>
Although this function throws an exception on invalid $time values (empty strings, for example), the exception can't be caught because it's a fatal exception. Use functions such as checkdate() and strtotime() to validate the string first. Example #1 should be changed to remove the try/catch block, since it's misleading.
There's a reason for ignoring the time zone when you pass a timestamp to __construct. That is, UNIX timestamps are by definition based on UTC. @1234567890 represents the same date/time regardless of time zone. So there's no need for a time zone at all.
A definite "gotcha" (while documented) that exists in the __construct is that it ignores your timezone if the $time is a timestamp. While this may not make sense, the object does provide you with methods to work around it.
<?php
// New Timezone Object
$timezone = new DateTimeZone('America/New_York');
// New DateTime Object
$date = new DateTime('@1306123200', $timezone);
// You would expect the date to be 2011-05-23 00:00:00
// But it actually outputs 2011-05-23 04:00:00
echo $date->format('Y-m-d H:i:s');
// You can still set the timezone though like so...
$date->setTimezone($timezone);
// This will now output 2011-05-23 00:00:00
echo $date->format('Y-m-d H:i:s');
?>
"The $timezone parameter and the current timezone are ignored when the $time parameter [...] is a UNIX timestamp."
Watch out - this means that these two are NOT equivalent, they result in different timezones (unless your current timezone is GMT):
<?php
$d = new DateTime(); $d->setTimestamp($t);
echo $o->format('O');
// +0200
$d = new DateTime('@' . $t);
echo $o->format('O');
// +0000
?>
Also forgot to mention, that MySQL "zeroed" dates do not throw an error but produce a non-sensical date:
<?php
$d = new DateTime("0000-00-00");
$d->format("Y-m-d"); // "-0001-11-30"
?>
Another good reason to write your own class that extends from DateTime.
The theoretical limits of the date range seem to be "-9999-01-01" through "9999-12-31" (PHP 5.2.9 on Windows Vista 64):
<?php
$d = new DateTime("9999-12-31");
$d->format("Y-m-d"); // "9999-12-31"
$d = new DateTime("0000-12-31");
$d->format("Y-m-d"); // "0000-12-31"
$d = new DateTime("-9999-12-31");
$d->format("Y-m-d"); // "-9999-12-31"
?>
Dates above 10000 and below -10000 do not throw errors but produce weird results:
<?php
$d = new DateTime("10019-01-01");
$d->format("Y-m-d"); // "2009-01-01"
$d = new DateTime("10009-01-01");
$d->format("Y-m-d"); // "2009-01-01"
$d = new DateTime("-10019-01-01");
$d->format("Y-m-d"); // "2009-01-01"
?>