Calculate next cron run date in PHP - php

Question

To preface this, I know cron-expression library exists. But I only need this one tiny bit for a quick display in a table in PHP. Also the library needs php 7.1 and I have to implement this on a php 5.3 site that doesn't really have composer set up.
So given this cron schedule
00 00 02,06,10,14,18,22 * * *
How do I calculate the next run date based on the current date?
I found another answer here on SO and it was working until it encountered the multiple explicit hours.
function calculate_next_cronjob($cronjob, $elementpositions)
{
$wildcard = false;
$elements = preg_split('/[^\d*]+/', $cronjob);
foreach (preg_split('/[^a-z]+/i', $elementpositions) as $key => $element) {
$value[$element] = $elements[$key];
switch ($element) {
case 's':
if ($value[$element] == '*') {
$value[$element] = date('s') + 1;
$wildcard = true;
}
break;
case 'i':
if ($value[$element] == '*') {
$value[$element] = date('i') + ($wildcard === true ? 0 : 1);
$wildcard = true;
}
break;
case 'H':
if ($value[$element] == '*') {
$value[$element] = date('H') + ($wildcard === true ? 0 : 1);
$wildcard = true;
}
break;
case 'd':
if ($value[$element] == '*') {
$value[$element] = date('d') + ($wildcard === true ? 0 : 1);
$wildcard = true;
}
if (intval($value[$element]) == 0) {
$value[$element] = 1;
}
break;
case 'm':
if ($value[$element] == '*') {
$value[$element] = date('m') + ($wildcard === true ? 0 : 1);
$wildcard = true;
}
if (intval($value[$element]) == 0) {
$value[$element] = 1;
}
break;
default:
unset($value[$element]);
}
}
$cy = date('Y');
$ny = $cy + 1;
if (time() < mktime($value['H'], $value['i'], $value['s'], $value['m'], $value['d'], $cy)) {
$value['Y'] = $cy;
} else {
$value['Y'] = $ny;
}
return date('Y-m-d H:i', mktime($value['H'], $value['i'], $value['s'], $value['m'], $value['d'], $value['Y']));
}
I imagine this function can be modified to account for this. I need help making those modifications.
Thank you