<?php
date.timezone = America/Los_Angeles
$start = new DateTime('2014-08-10');
$start->modify('first day of this month');
$end = new DateTime('2012-02-09');
$end->modify('first day of next month');
$interval = DateInterval::createFromDateString('1 month');
$period = new DatePeriod($start, $interval, $end);
foreach ($period as $dt) {
echo $dt->format("Y-m") . PHP_EOL;
}