adding two time values of similar formats using php

Question

i have two time values as give below

$time  = 06:58:00;
$time2 = 00:40:00;

I am doing this for calculating the appointments and available

Answer 1

Anudeep's solution was great for my use case, but I needed to be able to add negative times as well. Here's a slightly edited version of his code to take and return negative time strings ("-01:01:01" for example):

public static function sum_the_times($time1, $time2)
{
    $times = array($time1, $time2);
    $seconds = 0;
    $negative = false;
    foreach ($times as $time) {
        list($hour,$minute,$second) = explode(':', $time);
        if(substr($hour,0,1) == '-'){
            $seconds -= substr($hour,1)*3600;
            $seconds -= $minute*60;
            $seconds -= $second;
        } else {
            $seconds += $hour*3600;
            $seconds += $minute*60;
            $seconds += $second;
        }
    }
    if (substr($seconds, 0, 1) == '-') {
        $negative = true;
        $seconds = ($seconds * -1);
    }
    $hours = floor($seconds/3600);
    $seconds -= $hours*3600;
    $minutes  = floor($seconds/60);
    $seconds -= $minutes*60;
    if ($seconds < 9) {
        $seconds = "0".$seconds;
    }
    if ($minutes < 9) {
        $minutes = "0".$minutes;
    }
    if ($hours < 9) {
        $hours = "0".$hours;
    }
    return ($negative ? "-" : "")."{$hours}:{$minutes}:{$seconds}";
}