How to get last week' date range in PHP, Codeigniter, CakePHP

$previous_week = strtotime("-1 week +1 day");
$start_week = strtotime("last sunday midnight",$previous_week);
$end_week = strtotime("next saturday",$start_week);
$start_week = date("Y-m-d",$start_week);
$end_week = date("Y-m-d",$end_week);
echo $start_week.' '.$end_week ;