you could use explode() on a normally formatted time. For example:
$myTime = '21:32';
$hoursAndMinutes = explode(':', $myTime);
This will give you an indexed array, where key 0 has a value of '21', and key 1 has a value of '32';
Is that the sort of thing you're looking for?
Another option might be to find timestamps for the current time, and say, the opening time, and the closing time (today) with mktime, then just use > and < to find out if the time is within the desired range.