问在几周前的某个时候

EN

$array = array(...); // your input array
$start_time = new DateTime();
// Alternately, if you need week boundary to not be based on "now" 
// but rather on fixed start of week you could do something like
// $current_time = new DateTime('Monday this week 00:00:00');
$date_interval = new DateInterval('P1W');
$date_interval->invert = 1; // make it negative interval
// build DatePeriod object with 4 interval periods - don't include start date
$date_period = new DatePeriod($start_time, $date_interval, 4, DatePeriod::EXCLUDE_START_DATE);

$final_array = array(0,0,0,0); // the destination array with default start values
array_walk($array, function($item, $key_not_used) use ($date_period, $final_array) {
    // change date format as necessary below
    $item_time = DateTime::createFromFormat('y-m-d', $item['date']);
    $value = $item['value'];
    foreach($date_period as $i => $comparison_time) {
        if ($item_time > $comparison_time) {
            // aggregate this value into $final_array.
            // I assume this is simple addition but any sort of aggregation can be used by changing this line below
            $final_array[$i] = $final_array[$i] + $value;
            // break out of loop since comparison already completed
            break;
        }
    }
});
var_dump($final_array);

Array(
    [0] => ?, // aggregation for dates > 1 week ago
    [1] => ?, // aggregation for dates between 1 and 2 weeks ago
    [2] => ?, // aggregation for dates between 2 and 3 weeks ago
    [3] => ? // aggregation for dates between 3 and 4 weeks ago
)

$timestamp = strtotime($date);
$time_since_thursday = $timestamp % 604800;
$time_since_monday = ($time_since_thursday + 259200) % 604800;
$monday = $timestamp - $time_since_monday;

foreach($arrays as $array) {
  $difference = $monday - $array['date'];
  if ($difference > 0) { // else it would be in the same week or even later
    $difference_weeks = (int)($difference / 604800);
    if ($differenceWeeks <= 3) { // else it is more than the 4th week behind
      $month['week' . ($difference_weeks + 1)] += $array['value'];
    }
  }
}