months-options.php

<?php

$years = array_reverse(range(date('Y')-5, date('Y')));
$years = array_reduce(range(0, 60), function($months, $offset) {
	$utc = strtotime('-' . $offset . ' months');
	$offset % date('n') == 0 and $months += array(date('Y', $utc) => date('Y', $utc));
	$months += array(date('Y-m', $utc) => strtolower(date('Y - M', $utc)));
	return $months;
}, array());

/* Output:

Array
(
    [2014] => 2014
    [2014-05] => 2014 - may
    [2014-04] => 2014 - apr
    [2014-03] => 2014 - mar
    [2014-02] => 2014 - feb
    [2014-01] => 2014 - jan
    [2013] => 2013
    [2013-12] => 2013 - dec
    [2013-11] => 2013 - nov
    [2013-10] => 2013 - oct
    [2013-09] => 2013 - sep
    [2013-08] => 2013 - aug
    [2013-07] => 2013 - jul
    [2013-06] => 2013 - jun
    [2013-05] => 2013 - may
    [2013-04] => 2013 - apr
    [2013-03] => 2013 - mar
    ... etc
)
 **/