Question

I have a Unix timestamp like this:

$timestamp=1330581600

How do I get the beginning of the day and the end of the day for that timestamp?

e.g.
$beginOfDay = Start of Timestamp's Day
$endOfDay = End of Timestamp's Day

I tried this:

$endOfDay = $timestamp + (60 * 60 * 23);

But I don’t think it’ll work because the timestamp itself isn’t the exact beginning of the day.

Answer 1

strtotime can be used to to quickly chop off the hour/minutes/seconds

$beginOfDay = strtotime("today", $timestamp);
$endOfDay   = strtotime("tomorrow", $beginOfDay) - 1;

DateTime can also be used, though requires a few extra steps to get from a long timestamp

$dtNow = new DateTime();
// Set a non-default timezone if needed
$dtNow->setTimezone(new DateTimeZone('Pacific/Chatham'));
$dtNow->setTimestamp($timestamp);

$beginOfDay = clone $dtNow;
$beginOfDay->modify('today');

$endOfDay = clone $beginOfDay;
$endOfDay->modify('tomorrow');
// adjust from the start of next day to the end of the day,
// per original question
// Decremented the second as a long timestamp rather than the
// DateTime object, due to oddities around modifying
// into skipped hours of day-lights-saving.
$endOfDateTimestamp = $endOfDay->getTimestamp();
$endOfDay->setTimestamp($endOfDateTimestamp - 1);

var_dump(
    array(
        'time ' => $dtNow->format('Y-m-d H:i:s e'),
        'start' => $beginOfDay->format('Y-m-d H:i:s e'),
        'end  ' => $endOfDay->format('Y-m-d H:i:s e'),
    )
);

With the addition of extended time in PHP7, there is potential to miss a second if using $now <= $end checking with this.
Using $now < $nextStart checking would avoid that gap, in addition to the oddities around subtracting seconds and daylight savings in PHP’s time handling.