How to subtract minutes in PHP? - php

Question

I would like to know how to subtract two variables that represent minutes in PHP
For example I have two minute variables
$minutes1 = 20;
$minutes2 = 45;
$totalMinutes = $minutes1 -$minutes2;
//output should be 35 as $totalMinutes
An example would be
$time1 = "2:20";
$time2 = "3:45";
$finalTime = $time2 - $time1
//final time = 1:25
I am only interested in the minutes and not the hours

Answer 1

I bet that there's some cleaner way, but this seem to do what you're asking for.
$m1 = 20;
$m2 = 45;
$diff = $m1 - $m2;
echo $diff >= 0 ? $diff : $diff + 60;
This returns 35. Demo: https://3v4l.org/WaC8r

Answer 2

EDIT: Based on comments I have a better understanding of what you are asking for and have written this function.
function subtractMinutes($start, $sub) {
$res = $start;
while ($sub > 0) {
if ($sub >= 60) {
$sub -= 60;
continue;
}
if ($res >= $sub) {
$res -= $sub;
break;
}
if ($sub > $res) {
$sub -= $res + 1;
$res = 59;
continue;
}
$sub -= $res;
$res = 0;
}
return $res;
}
var_dump(subtractMinutes(20, 45)); //35
var_dump(subtractMinutes(20, 60)); //20
var_dump(subtractMinutes(20, 120)); //20
var_dump(subtractMinutes(20, 121)); //19
var_dump(subtractMinutes(40, 40)); //0
var_dump(subtractMinutes(59, 58)); //1

Answer 3

Please note that this answer attempts to provide a general solution.
If you only need to subtract a couple of times by all means, just
check with 60.
I would insist on suggesting you should be using decimals for all operations, and only turn into the correct format when outputting the result on a page. I believe it is safer to do calculations this way, instead of relying on you remembering to add/subtract 60 every time.
Examples:
$single_minute = 1.66;
$twenty_minutes = 20*1.66 = 33.2;
$sixty_minutes = 60*1.66 = 99.6;
When outputing:
$out_twenty = round(33.2/1.66);
$out_sixty = round(99.6/1.66);
You can use helper constants:
define("MINUTE", 1.66);
//You want to calculate 34 minutes
$thirtyfour_minutes = MINUTE * 34;
//You want to output 34 minutes
echo round($thirtyfour_minutes);