Recurring dates in PHP

recurring.php

<?php

require_once('When.php');

$_POST['weekly'] = true;
//array('MO','TU','WE','TH','FR','SA','SU')
$repeat_days = $_POST['selected_days'];
$repeat_type = isset($_POST['weekly']) ?: $_POST['monthly'];
//e.g 01/01/2013
$end = $_POST['end_date']; 

if($repeat_type == 'monthly') {
  $now = new DateTime();
  $end = $now->modify('+'. $_POST['no_of_months] .'month');
}

$w = new When();

$w->recur(new DateTime(), $repeat_type)
  ->until($end)
  ->byday($repeat_days);
                
while ($result = $w->next()) {
  $dates = $result->format("Y-m-d H:i:s");                  
}

var_dump($dates);
?>