如何在PHP中添加一分钟到DateTime（）对象？

Question

I am trying to make a time interval: $start to $end . But $start is always ending up the same as $end , as if they are both getting modified.

$dt = new \DateTime();
$start = $dt;
$end = $dt->modify('+1 minute');
echo $start->format('i') . ' - ' . $end->format('i');

This just gave me

50 - 50

When I want

49 - 50

What am I doing wrong?

Edit: I don't want to work with timestamps, only DateTime() objects.

Answer 1

Why this is happening

$start and $end both refer to the same object so when you add 1 minute to $dt both $start and $end will reflect the change.

What can you do

To fix, set $start and $end to new instances of the datetime object.

$dt = new \DateTime();
$start = new $dt;
$end = new $dt;
$end->modify('+1 minute');
echo $start->format('i') . ' - ' . $end->format('i');

Answer 2

An alternative to the already given answers would be to use

• DateTimeImmutable - This class behaves the same as DateTime except it never modifies itself but returns a new object instead.

Example:

$start = new \DateTimeImmutable();
$end = $start->modify('+1 minute');
echo $start->format('i') . ' - ' . $end->format('i');

This would give your expected result.

Answer 3

You create a single DateTime object $dt and then use the same object as both $start and $end . You should do one of the following:

$dt = new \DateTime();
$start = $dt->format('i'); //Store the actual string before modifying
$dt->modify('+1 minute'); 
echo $start . ' - ' . $end->format('i');

Or:

$start = new \DateTime();
$end = new \DateTime();    
$end->modify('+1 minute'); 
echo $start->format('i') . ' - ' . $end->format('i');