$a1 = explode(":",$arv);
		$a2 = explode(":",$arv2);
		$arv_x1 = mktime(0,trim($a1[0]),trim($a1[1]),0,0,0);
		$arv_x2 = mktime(0,trim($a2[0]),trim($a2[1]),0,0,0);
		$diff = $arv_x1 > $arv_x2 ? $arv_x1-$arv_x2 : $arv_x2-$arv_x1;
		$arv_ = date("G:s",$arv_x1+$diff);
		echo "$arv + $arv2 => $arv_ <br>";

output:3:28 + 3:28 => 0:28 
im trying to just get answer 6:56