รบกวนถามเรื่องบอกเวลาหน่อยครับ จะบวกกันแล้วคิดเป็นชม

$time1 = strtotime('2019-09-29 23:55:28');
$time2 = strtotime('2019-09-30 10:55:28');
echo date('Y-m-d H:i:s', ($time1+$time2));

<?php

$date1 = '2019-09-29 23:55:28';
$date2 = '2019-09-30 10:55:28';


echo '<meta charset="utf-8">' . PHP_EOL;
echo 'date1: ' . $date1 . '<br>' . PHP_EOL;
echo 'date2: ' . $date2 . '<br>' . PHP_EOL;


$DateTime1 = new \DateTime($date1);
$DateTime2 = new \DateTime($date2);

$diff = $DateTime1->diff($DateTime2);

var_dump($diff);
if ($diff->invert === 1) {
    echo 'Passed ';
}
echo $diff->format('%d Day and %h hours and %i minutes');
echo '<br>' . PHP_EOL;



function dateTimeAgo($dateTime1, $dateTime2)
{
    $DateTime1 = new \DateTime($dateTime1);
    $DateTime2 = new \DateTime($dateTime2);

    $Diff = $DateTime1->diff($DateTime2);

    $output = '';
    if ($Diff->invert === 1) {
        $output .= 'ผ่านไปแล้ว ';
    } else {
        $output .= 'กำลังจะถึงใน ';
    }

    $output .= $Diff->format('%d วัน %h ชั่วโมง and %i นาที %s วินาที');
    return $output;
}


echo dateTimeAgo($date1, $date2) . '<br>' . PHP_EOL;
echo '<hr>';



$date1 = '2019-09-29 23:55:27';
$date2 = '2019-10-02 10:55:28';
echo 'date1: ' . $date1 . '<br>' . PHP_EOL;
echo 'date2: ' . $date2 . '<br>' . PHP_EOL;
echo dateTimeAgo($date1, $date2) . '<br>' . PHP_EOL;
echo '<hr>';


$date1 = '2019-10-02 10:25:28';
$date2 = '2019-09-29 23:55:28';
echo 'date1: ' . $date1 . '<br>' . PHP_EOL;
echo 'date2: ' . $date2 . '<br>' . PHP_EOL;
echo dateTimeAgo($date1, $date2) . '<br>' . PHP_EOL;
echo '<hr>';


$date1 = '2019-10-02 10:35:48';
$date2 = '2019-09-29 23:55:28';
echo 'date1: ' . $date1 . '<br>' . PHP_EOL;
echo 'date2: ' . $date2 . '<br>' . PHP_EOL;
echo dateTimeAgo($date1, $date2) . '<br>' . PHP_EOL;
echo '<hr>';