为什么+3小时的另一个输出为+3小时？

Question

I am writing a small Time calculation. It should always add 3h to a given time.

But if i do "+3 h" in the method strtotime() in php it will output another value. So I wonder why "+3 hours" will work. Can somebody explain me why?

My php version is: 7.0.33-0ubuntu0.16.04.4

$date = "2019-05-04 15:00"; //format is Y-m-d H:i
$out = date("Y-m-d H:i", strtotime("+3 h", strtotime($date)));
echo $out; //out = 2019-05-04 14:00

$date = "2019-05-04 15:00"; //format is Y-m-d H:i
$out = date("Y-m-d H:i", strtotime("+3 hours", strtotime($date)));
echo $out; //out = 2019-05-04 18:00

This is a test example code from me. And $date is a different value every 15min.

PS: this is my first question on stackoverflow - Hello World :D

Answer 1

strtotime - Parse about any English textual datetime description into a Unix timestamp

You need to use hour OR hours. Similar for days you can use day or days.

$date = "2019-05-04 15:00"; //format is Y-m-d H:i
$out = date("Y-m-d H:i", strtotime("+3 h", strtotime($date)));
echo $out; //out = 2019-05-04 12:00

The output is showing 2019-05-04 12:00 not 2019-05-04 14:00.

It seems when you put the wrong format; ike +3 h, it's just subtracting that from the original time