(PHP 5 >= 5.3.0, PHP 7, PHP 8)
DateTimeInterface::diff -- DateTimeImmutable::diff -- DateTime::diff -- date_diff — Returns the difference between two DateTime objects
Object-oriented style
$targetObject, bool $absolute = false): DateInterval$targetObject, bool $absolute = false): DateIntervalProcedural style
$baseObject, DateTimeInterface $targetObject, bool $absolute = false): DateIntervalReturns the difference between two DateTimeInterface objects.
datetimeThe date to compare to.
absoluteShould the interval be forced to be positive?
The DateInterval object represents the difference between the two dates.
The return value more specifically represents the clock-time interval to
apply to the original object ($this or
$originObject) to arrive at the
$targetObject. This process is not always
reversible.
The method is aware of DST changeovers, and hence can return an interval of
24 hours and 30 minutes, as per one of the examples. If
you want to calculate with absolute time, you need to convert both the
$this/$baseObject, and
$targetObject to UTC first.
Example #1 DateTimeImmutable::diff() example
Object-oriented style
<?php
$origin = new DateTimeImmutable('2009-10-11');
$target = new DateTimeImmutable('2009-10-13');
$interval = $origin->diff($target);
echo $interval->format('%R%a days');
?>Procedural style
<?php
$origin = date_create('2009-10-11');
$target = date_create('2009-10-13');
$interval = date_diff($origin, $target);
echo $interval->format('%R%a days');
?>The above examples will output:
+2 days
Example #2 DateTimeInterface::diff() during DST changeover
<?php
$originalTime = new DateTimeImmutable("2021-10-30 09:00:00 Europe/London");
$targedTime = new DateTimeImmutable("2021-10-31 08:30:00 Europe/London");
$interval = $originalTime->diff($targedTime);
echo $interval->format("%H:%I:%S (Full days: %a)"), "\n";
?>The above example will output:
24:30:00 (Full days: 0)
Example #3 DateTimeInterface::diff() range
The value that the method returns is the exact amount of time to get from
$this to $targetObject.
Comparing January 1st to December 31st returns therefore 364, and not 365,
days (for non-leap years).
<?php
$originalTime = new DateTimeImmutable("2023-01-01 UTC");
$targedTime = new DateTimeImmutable("2023-12-31 UTC");
$interval = $originalTime->diff($targedTime);
echo "Full days: ", $interval->format("%a"), "\n";
?>The above example will output:
Full days: 364
Example #4 DateTime object comparison
Note:
DateTimeImmutable and DateTime objects can be compared using comparison operators.
<?php
$date1 = new DateTime("now");
$date2 = new DateTime("tomorrow");
var_dump($date1 == $date2);
var_dump($date1 < $date2);
var_dump($date1 > $date2);
?>The above example will output:
bool(false) bool(true) bool(false)