Date iteration PHP

$today = date('Y-m-d');

$date_start = $today
$date_end = date('Y-m-d', strtotime("{$date_start} + 30 days"));

while ($date_start != $date_end) {
echo "\n$date_start";
date_start = date('Y-m-d', strtotime("{date_start} + 1 day"));
}


===================
OUTPUT:
2009-12-01
2009-12-02
2009-12-03
.
.
.
and so on...