Level 53
using carbon it's easy:
$start = new \Carbon\Carbon('01-01-2018');
$end = new \Carbon\Carbon('31-01-2018');
$period = new DatePeriod($start, new DateInterval('P1W'), $end);
$weeks = [];
foreach($period as $week) {
if($week->endOfWeek() <= $end)
$weeks[] = $week->endOfWeek()->format('Y-m-d');
}
dd($weeks);