从现在起到X时间间隔15分钟填充时间下拉列表

I have 3 variables of type string that are always changing. Let's say they are currently:

$openTime = "10:00 am";
$closeTime = "1:00 pm";
$currentTime = "10:04 am";

How can I dynamically generate a dropdown that looks like:

<select>
    <option value="10:30 am">10:30 am</option>
    <option value="10:45 am">10:45 am</option>
    ...
    <option value="1:00 pm">1:00 pm</option>
</select>

without JS?

Note that the first option isn't 10:15 am because currentTime + 15 minutes = 10:19 am which is past 10:15 am.