CODEWITHSUNDEEP
phptimestampstrtotime
baudot
baudot

Reputation: 1618

Dividing timestamps into weeks

I'm looking to divide a span between two timestamps into weeks, in PHP.

Essentially, what I want to do is:

function divide_into_weeks($start_time, $end_time) {
  // Iterate back from the end time,
  // creating an array of timestamps broken into calendar weeks.
  $done = FALSE;
  $divider = $end_time;
  for ($i = 0; !$done; $i++) {
    $timeslots[$i]->end = $divider;
    // Set the start time to the start of the current week.
    $timeslots[$i]->start = strtotime("monday this week", $divider);
    if ($timeslots[$i]->start <= $start_time) {$done = TRUE;}
    // If we loop again, end the previous week one second before the start of this week.
    $divider = $timeslots[$i]->start - 1;
  }
}

However, the function hits an infinite loop.

Why? Because...

strtotime("monday this week", $monday_of_next_week -1) == $monday_of_last week;

... is true, strangely. This is unlike other strtotime operations I've tested. In other cases, you knock a second off, repeat, and it iterate back by one of whatever unit you've asked for. But not for Monday (or Sunday) of this week.

For example:

$today = strtotime("midnight");
$yesterday = strtotime("midnight", $today -1);

...produces sensible results.

But my attempts to use the same technique with "monday of this week" or "sunday of this week" have proven fruitless, so far.

So, can someone show how to iterate timestamps back by weeks?

Upvotes: 0

Views: 178

Answers (2)

Glavić
Glavić

Reputation: 43572

I think this would help you:

function divide_into_weeks($start_time, $end_time, $tz) {
    $tz    = new DateTimezone($tz);
    $start = new DateTime("@$start_time");
    $end   = new DateTime("@$end_time");
    $start ->setTimezone($tz)->modify($start->format('o-\WW-1 00:00:00'));
    $end   ->setTimezone($tz)->modify($end  ->format('o-\WW-7'));
    $weeks = [];

    do {
        $weeks[] = [
            'start' => clone $start,
            'end' => new DateTime($start->format('o-\WW-7 23:59:59'), $tz),
        ];
        $start->modify('+7 day');
    } while ($start < $end);

    return $weeks;
}

demo

Upvotes: 1

baudot
baudot

Reputation: 1618

This ended up being the workaround that did the trick: (With some of the irrelevant bits trimmed.) 

function divide_timespan_into_units($start_second, $end_second, $time_unit) {
  $timeslots = array();
  // The time_formatter guides strtotime in what parts of a timestamp to trim off to leave timestamps split on calendar divisions.
  switch ($time_unit) {
    case "hour":
      $time_formatter = 'Y-m-d H:00:00';
      break;
    case "day":
      $time_formatter = 'Y-m-d 00:00:00'; 
      break;
    case "week":
      $time_formatter = "monday this week"; 
      break;
  }

  $done = FALSE;
  $divider = $end_second;

  for ($i = 0; !$done; $i++) {
    $timeslots[$i] = (object) array('end' => $divider);
    if ($time_unit == "week") {
      // Dividing timestamps up into calendar weeks requires special handling. 
      //
      // Note on the strange constants "86399" & "86400" in the two lines following:
      // This is a workaround for a fluke in how strtotime treats weeks:
      // 
      // strtotime can't decide if Sunday or Monday is the start of the week.
      // You have to force it by rolling back a full day plus one second from the start of Monday, to get into the previous week.
      //
      // Simply rolling back a second from Sunday by 1 second doesn't get you into the previous week,
      // because if you ask for "this Sunday" on any day other than Sunday, it will return the coming Sunday, not the past Sunday.
      // However, if you back up 1 second from the stroke of midnight Monday, and ask what week you're in, 
      // you'll be told that you're still in the same week.
      //
      // This nudge of an extra 86400 seconds (a full extra day) back and forth forces the week to click over.
      //
      // This will likely be settled in a later version of PHP, but as of 5.3.5 (when this is being coded) it's an issue.
      $timeslots[$i]->start = strtotime("monday this week", $divider-86400);
      $divider = $timeslots[$i]->start+86399;
    } else {
      $timeslots[$i]->start = strtotime(date($time_formatter, $divider));
    }
    if ($timeslots[$i]->start <= $start_second) {$done = TRUE;}
    $divider = $timeslots[$i]->start - 1;
  }
}

Upvotes: 0

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