- explode: documentation ( source)
<?php
$addTime = explode('+','2013-03-28T13:15:00+05:30');
list($hours, $minutes) = explode(':', $addTime[1]);
$dt = new DateTime('2013-03-28T13:15:00+05:30');
$dt->add(new DatePeriod('PT'.$hours.'H'));
$dt->add(new DatePeriod('PT'.$minutes.'M'));
echo $dt->format('Y-m-d H:i:s');