DateInterval

$year=date('Y');
$from = new DateTime($year.'-09-01 08:00:00');
$to   = new DateTime($year.'-09-01 21:00:00');
$to->modify('+52 week');
$period = new DatePeriod($from, new DateInterval('P1D'), $to);
$period=iterator_to_array($period);
$aWeek=array();
$start=false;
for($i=0,$size=sizeof($period);$i<$size;++$i){
    $w=$period[$i]->format('w');
    $d[]=$period[$i]->format('Y-m-d H:i:s');
    if(!$start)$start=$period[$i]->format('Y-m-d H:i:s');
    if($w==0)$end=$period[$i]->format('Y-m-d H:i:s');
    if($start && $end){
        $aWeek[]=['r'=>array($start,$end),'d'=>$d];
        unset($start,$end,$d);
    }

}