PHP Program to get time difference

<?php
$time1 = "09:00";
$time2 = "17:00";

function get_time_difference($time1, $time2)
{
    $time1 = strtotime($time1);
    $time2 = strtotime($time2);

    if ($time2 < $time1)
    {
        $time2 += 86400;
    }

    return date("H:i", strtotime("00:00") + ($time2 - $time1));
}

$timediff = get_time_difference($time1, $time2); // 12:15:29
printf("Difference between in time : " . $timediff);
print "</br>";
?>

Output
Difference between in time : 08:00