<?php
function timetoTime($time) {
	$timeArr = array_reverse(explode(":", $time));
	$seconds = 0;
	foreach ($timeArr as $key => $value) {
		if ($key > 2) break;
		$seconds += pow(60, $key) * $value;
	}
	return $seconds;
}
$tarih1 	= timetoTime('35:30');
$tarih2 	= timetoTime('01:50');
$tarihson 	= gmdate($tarih1+$tarih2);
?>

$tarihson	= $tarih1 + $tarih2;
echo ($tarihson >= 3600) ? gmdate('H:i:s',$tarihson):gmdate('i:s',$tarihson);