使用strtotime的时差

Question

This shouldn't be hard, but still I don't understand what is happening.

<?php
    echo date( 'H:i', strtotime( '09:00' ) - strtotime( '08:00' ) ); 
    // returns 02:00 instead of 01:00

    echo date( 'H:i', strtotime( '18:45' ) - strtotime( '17:15' ) ); 
    // returns 02:30 instead of 01:30

    echo date( 'H:i', strtotime( '17:00' ) - strtotime( '09:00' ) );
    // returns 09:00 instead of 08:00

What is adding the extra hour?

So maybe I need to add a date?

<?php
    echo date( 'H:i', strtotime( '22-09-2016 17:00:00' ) - strtotime( '22-09-2016 09:00:00' ) );
    // still 09:00 instead of 08:00

Some extra information

I am using Laravel en tested in Xampp.

In Laravel /config/app.php 'timezone' => 'Europe/Amsterdam',

In Xampp date_default_timezone_set('Europe/Amsterdam');

Still no difference.

This calculation is done in the blade template where I cannot access the DateTime class.

I found a way to use the DateTime class. Another solution was changing the timezone to UTC, but then all my other timestamps are wrong.

Answer 1

find difference using DateTime object like

$time1 = new DateTime('18:45');
$time2 = new DateTime('17:15');
$interval = $time1->diff($time2);
echo $interval->format('%H:%I');