DateTimeInterface::diff
(PHP 5 >= 5.3.0, PHP 7, PHP 8)
Returns the difference between two DateTime objects
Description
Oop
Procedural
Returns the difference between two DateTimeInterface objects.
Parameters
datetimeThe date to compare to.
absoluteShould the interval be forced to be positive?
Return Values
The DateInterval object represents the difference between the two dates.
The absolute parameter only affects the invert property of a DateInterval object.
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.
Examples
DateTimeImmutable::diff() example
Oop
<?php
$origin = new DateTimeImmutable('2009-10-11');
$target = new DateTimeImmutable('2009-10-13');
$interval = $origin->diff($target);
echo $interval->format('%R%a days');The above example will output:
+2 daysProcedural
<?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 example will output:
+2 daysDateTimeInterface::diff during DST changeover
<?php
$originalTime = new DateTimeImmutable("2021-10-30 09:00:00 Europe/London");
$targetTime = new DateTimeImmutable("2021-10-31 08:30:00 Europe/London");
$interval = $originalTime->diff($targetTime);
echo $interval->format("%H:%I:%S (Full days: %a)"), "\n";The above example will output:
24:30:00 (Full days: 0)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");
$targetTime = new DateTimeImmutable("2023-12-31 UTC");
$interval = $originalTime->diff($targetTime);
echo "Full days: ", $interval->format("%a"), "\n";The above example will output:
Full days: 364DateTime object comparison
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)