- substr: documentation ( source)
<?php
$start = new DateTime('2010-12-02');
$start->modify('first day of this month');
$end = new DateTime('2012-05-06');
$end->modify('first day of next month');
$interval = DateInterval::createFromDateString('1 month');
$period = new DatePeriod($start, $interval, $end);
$dateStr = '';
foreach ($period as $dt) {
$dateStr = $dateStr . "'". $dt->format("Y-m")."-01'".", ";
}
$dateStr = substr($dateStr, 0, -2);
echo $dateStr;