<?php

function calculate_hours ($array)
{

	$time1 			= "";
	$time2 			= "00:00:00";
	$time1_seconds 	= 0;
	$time2_seconds 	= 0;
	$sum_hours 		= 0;
	$sum_mins 		= 0;
	$sum_secs 		= 0;
	$is_negative 	= false;
	$type 			= "";

	sscanf($time2, "%d:%d:%d", $hours2, $minutes2, $seconds2);

	$time2_seconds = isset($seconds2)
		? $hours2 * 3600 + $minutes2 * 60 + $seconds2
		: $hours2 * 60 + $minutes2;

	foreach ($array as $time):

		$type = key($time);
		$time1 = $time[$type] . ":00";

		sscanf($time1, "%d:%d:%d", $hours1, $minutes1, $seconds1);

		$time1_seconds = isset($seconds1)
			? $hours1 * 3600 + $minutes1 * 60 + $seconds1
			: $hours1 * 60 + $minutes1;

		$time2_seconds = ($type === "+")
			? ($time1_seconds + $time2_seconds)
			: ($time2_seconds - $time1_seconds);

	endforeach;

	$is_negative = ($time2_seconds < 0)
		? true
		: false;

	$sum_hours 	= ($is_negative === true)
		? ceil($time2_seconds / 3600)
		: floor($time2_seconds / 3600);

	$sum_mins 	= ($is_negative === true)
		? ceil($time2_seconds / 60 % 60)
		: floor($time2_seconds / 60 % 60);

	$sum_secs 	= ($is_negative === true)
		? ceil($time2_seconds % 60)
		: floor($time2_seconds % 60);

	$sum_hours = str_pad(abs($sum_hours), 2, "0", STR_PAD_LEFT);
	$sum_mins = str_pad(abs($sum_mins), 2, "0", STR_PAD_LEFT);
	$sum_secs = str_pad(abs($sum_secs), 2, "0", STR_PAD_LEFT);

	$time2 = ($is_negative)
		? "-{$sum_hours}:{$sum_mins}"
		: "+{$sum_hours}:{$sum_mins}";

	return $time2;

}

echo calculate_hours (array
(
	array
	(
		"+" => "10:00"
	),
	array
	(
		"-" => "05:45"
	),
	array
	(
		"+" => "00:01"
	),
));