php gets the start and end time of each week and month between the specified dates, php date_PHP tutorial

class Datefmt{
   function __construct() {}
  /**
* Get the start time and end time of the week based on the specified date
​*/
  public function get_weekinfo_by_date($date) {
    $idx = strftime("%u", strtotime($date));
    $mon_idx = $idx - 1;
    $sun_idx = $idx - 7;
    return array(
      'week_start_day' => strftime('%Y-%m-%d', strtotime($date) - $mon_idx * 86400),
      'week_end_day' => strftime('%Y-%m-%d', strtotime($date) - $sun_idx * 86400),
      );
  }
  /**
* Get the start time and end time of the month based on the specified date
​*/
  public function get_monthinfo_by_date($date){
    $ret = array();
    $timestamp = strtotime($date);
    $mdays = date('t', $timestamp);
    return array(
      'month_start_day' => date('Y-m-1', $timestamp),
      'month_end_day' => date('Y-m-'.$mdays, $timestamp)
      );
  }
  /**
* Get the weeks between the specified dates
​*/
  public function get_weeks($sdate, $edate) {
    $range_arr = array();
    // 检查日期有效性
    $this->check_date(array($sdate, $edate));
    // 计算各个周的起始时间
    do {
      $weekinfo = $this->get_weekinfo_by_date($sdate);
      $end_day = $weekinfo['week_end_day'];
       $start = $this->substr_date($weekinfo['week_start_day']);
      $end = $this->substr_date($weekinfo['week_end_day']);
      $range = "{$start} ~ {$end}";
      $range_arr[] = $range;
       $sdate = date('Y-m-d', strtotime($sdate)+7*86400);
    }while($end_day < $edate);
    return $range_arr;
  }
  /**
* Get each month between the specified dates
​*/
  public function get_months($sdate, $edate) {
    $range_arr = array();
    do {
      $monthinfo = $this->get_monthinfo_by_date($sdate);
      $end_day = $monthinfo['month_end_day'];
       $start = $this->substr_date($monthinfo['month_start_day']);
      $end = $this->substr_date($monthinfo['month_end_day']);
      $range = "{$start} ~ {$end}";
      $range_arr[] = $range;
       $sdate = date('Y-m-d', strtotime($sdate.'+1 month'));
    }while($end_day < $edate);
    return $range_arr;
  }
  /**
* The month and day in the intercepted date
* @param string $date
* @return string $date
​*/
  public function substr_date($date) {
    if ( ! $date) return FALSE;
    return date('m-d', strtotime($date));
  }
  /**
* Check date validity YYYY-mm-dd
* @param array $date_arr
* @return boolean
​*/
  public function check_date($date_arr) {
    $invalid_date_arr = array();
    foreach ($date_arr as $row) {
      $timestamp = strtotime($row);
      $standard = date('Y-m-d', $timestamp);
      if ($standard != $row) $invalid_date_arr[] = $row;
    }
    if ( ! empty($invalid_date_arr)) {
      die("invalid date -> ".print_r($invalid_date_arr, TRUE));
    }
  }
}

​ require_once "Datefmt.class.php";
$datefmt = new Datefmt();
// Output the weeks between November 1st and 30th
var_dump($datefmt->get_weeks('2014-11-05', '2014-11-29'));
/*The result is
array(4) {
[0]=>
String(13) "11-03 ~ 11-09"
[1]=>
String(13) "11-10 ~ 11-16"
[2]=>
String(13) "11-17 ~ 11-23"
[3]=>
String(13) "11-24 ~ 11-30"
}
*/
// Output February 1st and November 30th
var_dump($datefmt->get_months('2014-02-03', '2014-11-29'));
/*The result is
array(10) {
[0]=>
String(13) "02-01 ~ 02-28"
[1]=>
String(13) "03-01 ~ 03-31"
[2]=>
String(13) "04-01 ~ 04-30"
[3]=>
String(13) "05-01 ~ 05-31"
[4]=>
String(13) "06-01 ~ 06-30"
[5]=>
String(13) "07-01 ~ 07-31"
[6]=>
String(13) "08-01 ~ 08-31"
[7]=>
String(13) "09-01 ~ 09-30"
[8]=>
String(13) "10-01 ~ 10-31"
[9]=>
String(13) "11-01 ~ 11-30"
}
*/