/**
* 判断两日期是不是同一周
* 星期是按周日到周六
*/
function getSameWeek($pretime,$aftertime){
    $flag = false;//默认不是同一周
    $afweek = date('w',$aftertime);//当前是星期几
    $mintime = $aftertime - $afweek * 3600*24;//一周开始时间
    $maxtime = $aftertime + (7-$afweek)*3600*24;//一周结束时间
    if ( $pretime >= $mintime && $pretime <= $maxtime){//同一周
      $flag = true;
    }
    return $flag;
}
$testWeek_start=strtotime('2017-8-19');
$testWeek_end=strtotime('2017-8-23');
echo getSameWeek($testWeek_start,$testWeek_end)?'在同一周':'不在同一周';