使用\DateTime和\DateInterval执行计算：

$date1 = new \DateTime('now', new DateTimeZone('UTC'));
$date2 = new \DateTime('now', new DateTimeZone('UTC'));
$time1 = new \DateInterval('PT76H');
$time2 = new \DateInterval('PT30H');

$date1->add($time1);
$date2->add($time2);

$diff = $date1->diff($date2);
echo ($diff->days * 24 + $diff->h) . $diff->format(':%I:%S');

说明：无法直接在DateInterval上执行计算，因此您必须创建日期作为计算的基础。然后将两个不同的间隔添加到当前日期，并计算它们之间的差值。diff()返回包含总天数的\DateInterval，您必须将总天数乘以24才能获得小时数，以及不构成完整天数的小时数。
编辑：时区应指定为UTC，以避免夏令时问题。

• • 你可以试试这个：**

/**
 * Common method to diff between two time
 * 
 * @param string $start
 * @param string $end
 * @return string
 */
public function diffTime($start, $end)
{
    /* $start = '76:00:00'; */
    /* $end = '30:00:00'; */
    /* Get total time in Seconds */
    $totalStartTimeSec = self::getTotalSeconds($start);
    $totalEndTimeSec = self::getTotalSeconds($end);
    /* Get difference time in Seconds */
    $difference = abs($totalStartTimeSec - $totalEndTimeSec);
    $hours = floor($difference / 3600);
    $minutes = floor(($difference % 3600) / 60);
    $seconds = $difference % 60;
    $diffFormat = str_pad($hours, 2, '0', STR_PAD_LEFT). ":" . str_pad($minutes, 2, '0', STR_PAD_LEFT). ":" . str_pad($seconds, 2, '0', STR_PAD_LEFT);
    
    /* result $diffFormat is '46:00:00'; */
    return $diffFormat;
}

/**
 * Get total time in Seconds
 * 
 * @param string $time
 * @return array
 */
public function getTotalSeconds($time) {
    $timeArr = explode(':', $time);
    $allTime = [];
    if (isset($timeArr[0]) && $timeArr[0] > 24) {
        $greaterDuration = $timeArr[0];
        while ($greaterDuration > 24) {
            $greaterDuration -= 24;
            $allTime[] = strtotime('24:00:00') - strtotime('00:00');
        }
        if ($greaterDuration == 24 && ($timeArr[1] != '00' || $timeArr[2] != '00')) {
            $greaterDuration -= 24;
            $allTime[] = strtotime('24:00:00') - strtotime('00:00');
        }
        $remainingTime = str_pad($greaterDuration, 2, '0', STR_PAD_LEFT) . ':' . $timeArr[1] . ':' . $timeArr[2];
        $allTime[] = strtotime($remainingTime) - strtotime('00:00');
    } else {
        $allTime[] = strtotime($time) - strtotime('00:00');
    }
    
    return array_sum($allTime);
}

谢谢!