- explode: documentation ( source)
<?php
$addTime = explode('+','2013-03-28T13:15:00+05:30');
list($hours, $minutes) = explode(':', $addTime[1]);
$dt = new DateTime($addTime[0]);
$dt->add(new DateInterval('PT'.intval($hours).'H'));
$dt->add(new DateInterval('PT'.intval($minutes).'M'));
echo $dt->format('Y-m-d H:i:s');