Recipe 3.15 Generating Time Ranges
3.15.1 Problem
You need to know all the days in a
week or a month. For example, you want to print out a list of
appointments for a week.
3.15.2 Solution
Identify your start date using time(
)
and strftime( ). If
your interval has a fixed length, you can loop through that many
days. If not, you need to test each subsequent day for membership in
your desired range.
For example, a week has seven days, so you can use a fixed loop to
generate all the days in the current week:
// generate a time range for this week
$now = time();
// If it's before 3 AM, increment $now, so we don't get caught by DST
// when moving back to the beginning of the week
if (3 < strftime('%H', $now)) { $now += 7200; }
// What day of the week is today?
$today = strftime('%w', $now);
// How many days ago was the start of the week?
$start_day = $now - (86400 * $today);
// Print out each day of the week
for ($i = 0; $i < 7; $i++) {
print strftime('%c',$start_day + 86400 * $i);
}
3.15.3 Discussion
A particular month or year
could have a variable number of days, so you need to compute the end
of the time range based on the specifics of that month or year. To
loop through every day in
a month, find the epoch timestamps for the first day of the month and
the first day of the next month. The loop variable,
$day is incremented a day at a time (86400
seconds) until it's no longer less than the epoch
timestamp at the beginning of the next month:
// Generate a time range for this month
$now = time();
// If it's before 3 AM, increment $now, so we don't get caught by DST
// when moving back to the beginning of the month
if (3 < strftime('%H', $now)) { $now += 7200; }
// What month is this?
$this_month = strftime('%m',$now);
// Epoch timestamp for midnight on the first day of this month
$day = mktime(0,0,0,$this_month,1);
// Epoch timestamp for midnight on the first day of next month
$month_end = mktime(0,0,0,$this_month+1,1);
while ($day < $month_end) {
print strftime('%c',$day);
$day += 86400;
}
3.15.4 See Also
Documentation on time( ) at
http://www.php.net/time and strftime(
) at http://www.php.net/strftime.
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