php 获取本周一 时间

function this_monday($timestamp=0,$is_return_timestamp=true){      static $cache ;      $id = $timestamp.$is_return_timestamp;      if(!isset($cache[$id])){          if(!$timestamp) $timestamp = time();          $monday_date = date('Y-m-d', $timestamp-86400*date('w',$timestamp)+(date('w',$timestamp)>0?86400:-/*6*86400*/518400));          if($is_return_timestamp){              $cache[$id] = strtotime($monday_date);          }else{              $cache[$id] = $monday_date;          }      }      return $cache[$id];      }

PHP 获取本周一时间