how to calculate a difference between two Zend_Date objects, in months

Question

I have two objects of Zend_Date class and I want to calculate the difference between them in full calendar months.. How can I do this?

<?php
$d1 = new Zend_Date('1 Jan 2008');    
$d2 = new Zend_Date('1 Feb 2010');
$months = $d1->sub($d2)->get(Zend_Date::MONTH);
assert($months == -25); // failure here

Thanks in advance!

Answer 1

If I read the docs correctly, there's no implemented functionality for getting difference between 2 dates in seconds/minutes/.../months/years, so you'll need to calculate it yourself. Something like this will do (dunno if it takes leap years, DST and such into consideration):

<?php
$d1 = new Zend_Date('1 Jan 2008');    
$d2 = new Zend_Date('1 Feb 2010');
$diff = $d1->sub($d2)->toValue();
$months = floor(((($diff/60)/60)/24)/30);