public function getIntervals()
{
    $intervals = array();
    $formatHigh = 'Y-m-d 23:59:59';
    switch ($this->step) {
        case self::STEP_DAYS:
            $formatLow = 'Y-m-d 00:00:00';
            $lowestDate = date($formatLow, $this->from);
            $highestDate = date($formatHigh, $this->to);
            $currentDate = date($formatLow, $this->from);
            while ($currentDate < $highestDate) {
                $low = $currentDate;
                $high = date($formatHigh, strtotime($currentDate));
                $currentDate = date($formatLow, strtotime('+1 day', strtotime($currentDate)));
                $intervals[] = compact('low', 'high');
            }
            break;
        case self::STEP_WEEKS:
            $formatLow = 'Y-m-d 00:00:00';
            $lowestDate = date($formatLow, $this->from);
            $highestDate = date($formatHigh, $this->to);
            if ($this->step_mode == self::STEP_MODE_STANDARD) {
                $year = date('Y', $this->from);
                $week = date('W', $this->from);
                $currentDate = date($formatLow, strtotime(sprintf('%s-W%s', $year, $week)));
                while ($currentDate < $highestDate) {
                    $low = $currentDate;
                    $currentDate = date($formatLow, strtotime('+1 week', strtotime($currentDate)));
                    $high = date($formatHigh, strtotime(sprintf('%s - 1 day', $currentDate)));
                    $intervals[] = compact('low', 'high');
                }
            } else { //self::STEP_MODE_INTERVAL
                $currentDate = date($formatLow, $this->from);
                while ($currentDate < $highestDate) {
                    $low = $currentDate;
                    $currentDate = date($formatLow, strtotime('+7 days', strtotime($currentDate)));
                    $high = date($formatHigh, strtotime(sprintf('%s - 1 day', $currentDate)));
                    $intervals[] = compact('low', 'high');
                }
            }
            break;
        case self::STEP_MONTHS:
            if ($this->step_mode == self::STEP_MODE_STANDARD) {
                $formatLow = 'Y-m-01 00:00:00';
                $lowestDate = date($formatLow, $this->from);
                $currentDate = $lowestDate;
                $highestDate = date($formatHigh, strtotime(sprintf(
                    'last day of %s %d',
                    date('F', $this->to),
                    date('Y', $this->to)
                )));
                while ($currentDate < $highestDate) {
                    $tsCurrentDate = strtotime($currentDate);
                    $low = $currentDate;
                    $high = date($formatHigh, strtotime(sprintf(
                        'last day of %s %d -1 day',
                        date('F', $tsCurrentDate),
                        date('Y', $tsCurrentDate)
                    )));
                    $intervals[] = compact('low', 'high');
                    $currentDate = date($formatLow, strtotime('+1 month', strtotime($currentDate)));
                }
            } else { //self::STEP_MODE_INTERVAL
                $formatLow = 'Y-m-d 00:00:00';
                $currentDate = date($formatLow, $this->from);
                $highestDate = date($formatHigh, $this->to);
                while ($currentDate < $highestDate) {
                    $low = $currentDate;
                    $currentDate = date($formatLow, strtotime('+30 days', strtotime($currentDate)));
                    $high = date($formatHigh, strtotime(sprintf('%s - 1 day', $currentDate)));
                    $intervals[] = compact('low', 'high');
                }
            }
            break;
        case self::STEP_YEARS:
            if ($this->step_mode == self::STEP_MODE_STANDARD) {
                $formatLow = 'Y-01-01 00:00:00';
                $lowestDate = date($formatLow, $this->from);
                $currentDate = $lowestDate;
                $highestDate = date($formatHigh, $this->to);
                while ($currentDate < $highestDate) {
                    $low = $currentDate;
                    $currentDate = date($formatLow, strtotime('+1 year', strtotime($currentDate)));
                    $high = date($formatHigh, strtotime(sprintf('%s - 1 day', $currentDate)));
                    $intervals[] = compact('low', 'high');
                }
            } else { //self::STEP_MODE_INTERVAL
                $formatLow = 'Y-m-d 00:00:00';
                $lowestDate = date($formatLow, $this->from);
                $currentDate = $lowestDate;
                $highestDate = date($formatHigh, $this->to);
                while ($currentDate < $highestDate) {
                    $low = $currentDate;
                    $currentDate = date($formatLow, strtotime('+365 days', strtotime($currentDate)));
                    $high = date($formatHigh, strtotime(sprintf('%s - 1 day', $currentDate)));
                    $intervals[] = compact('low', 'high');
                }
            }
            break;
    }
    if (empty($intervals) === false) {
        if ($intervals[0]['low'] < $lowestDate) {
            $intervals[0]['low'] = $lowestDate;
        }
        end($intervals);
        $lastIntervalsKey = key($intervals);
        if ($intervals[$lastIntervalsKey]['high'] > $highestDate) {
            $intervals[$lastIntervalsKey]['high'] = $highestDate;
        }
        reset($intervals);
    }
    return $intervals;
}