php 获取当前日期往前推一周的时间

$week_price_list = [];
for ($datetime = time(); $datetime > time() - 86400*7; $datetime = $datetime - 86400) {
   $date = date('Y-m-d', $datetime);
   $price = Cache::store('redis')->handler()->ZSCORE('hxyg_btc_price',$date);
   if ($price) {
      $week_price_list[$date] = $price;
   }
}
ksort($week_price_list);