尝试使用dateTime类以GMT，PST和EST显示当前时间

Question

I have attempted to do this using the following code:

$date = new DateTime('now');

$datePST = $date->setTimezone(new DateTimezone('PST'));

$dateEST = $date->setTimezone(new DateTimezone('EST'));

echo $date->format('H:i:s');
echo '<br />';
echo $EST = $dateEST->format('H:i:s');
echo '<br />';
echo $PST = $datePST->format('H:i:s');

But they all output the same time. Why are they not outputting the correct times?

Answer 1

Because they are all pointing to the same object. So when you change the timezone in one you are changing it for all of them.

$date = new DateTime('now');
echo $date->format('H:i:s');
echo '<br />';
$date->setTimezone(new DateTimezone('PST'));
echo $date->format('H:i:s');
echo '<br />';
$date->setTimezone(new DateTimezone('EST'));
echo $date->format('H:i:s');

If you want to have separate variables for each timezone you can use clone to create new objects:

$date = new DateTime('now');
$datePST = clone $date;
$datePST = $datePST->setTimezone(new DateTimezone('PST'));
$dateEST = clone $date;
$dateEST = $dateEST->setTimezone(new DateTimezone('EST'));

echo $date->format('H:i:s');
echo '<br />';
echo $EST = $dateEST->format('H:i:s');
echo '<br />';
echo $PST = $datePST->format('H:i:s');

If you're using PHP 5.5 you can use the new DateTimeImmutatable() class as well:

$date = new DateTimeImmutable('now');
$datePST = $date->setTimezone(new DateTimezone('PST'));
$dateEST = $date->setTimezone(new DateTimezone('EST'));

FYI, using "now" is unnecessary as when no parameter is passed to DateTime() it automatically defaults to the current date and time..