How to get the first day of the current year?

I need to use PHP DateTime to get the first day of the current year. I've tried:

$year = new DateTime('first day of this year');
var_dump($year);

But this seems to be returning the first day of the current month: 2014-09-01 09:28:56

Why? How do I correctly get the first day of the current year?

Your relative date format 'first day of this year' is correct by returning the first day of the month because of the definition of first day of:

Sets the day of the first of the current month. This phrase is best used together with a month name following it. (See PHP-doc)

To get the first day of the current year with the relative format you can use something like this:

'first day of January ' . date('Y')

Or use only text in the strtotime function:

date('Y-m-d', strtotime('first day of january this year'));