$time1 = "23:58";
$time2 = "01:00";
$time1 = explode(':',$time1);
$time2 = explode(':',$time2);
$hours1 = $time1[0];
$hours2 = $time2[0];
$mins1 = $time1[1];
$mins2 = $time2[1];
$hours = $hours2 - $hours1;
$mins = 0;
if($hours < 0)
{
$hours = 24 + $hours;
}
if($mins2 >= $mins1) {
$mins = $mins2 - $mins1;
}
else {
$mins = ($mins2 + 60) - $mins1;
$hours--;
}
if($mins < 9)
{
$mins = str_pad($mins, 2, '0', STR_PAD_LEFT);
}
if($hours < 9)
{
$hours =str_pad($hours, 2, '0', STR_PAD_LEFT);
}
echo $hours*60+$mins;
другой метод
$to_time = strtotime("01:47:00");
$from_time = strtotime(" 01:55:00");
echo round(abs($to_time - $from_time) / 60). " minute";