- var_dump: documentation ( source)
<?php
$d = new DateTime('2014-08-09');
var_dump($d->format('Y -- W -- w'));
$d = new DateTime('2014-08-10');
var_dump($d->format('Y -- W -- w'));
$d = new DateTime('2014-08-11');
var_dump($d->format('Y -- W -- w'));