https://www.hackerrank.com/challenges/a-very-big-sum

HR problem solution

<?php
function getSum($first, $second){
    // reverse the inputs
    $reversed_first = strrev($first);
    $reversed_second = strrev($second);
    // get the max string length
    $length = strlen($reversed_first) > strlen($reversed_second) ? strlen($reversed_first) : strlen($reversed_second);
    // carry will be zero initially
    $carry = 0;
    // sum array for storing the 
    $sum = [];
    for($i = 0; $i < $length; ++$i){
    	$current_sum = (isset($reversed_first[$i]) ? $reversed_first[$i] : 0) + (isset($reversed_second[$i]) ? $reversed_second[$i] : 0) + $carry;
    	$carry = (int) $current_sum/10;
    	$sum[] = $current_sum%10;
    }
	return strrev(implode("", $sum));
}

$handle = fopen ("php://stdin","r");
fscanf($handle,"%d",$n);
$arr_temp = fgets($handle);
$arr = explode(" ",$arr_temp);
$sum = $arr[0];
for($i = 1; $i < count($arr); ++$i){
	$sum = getSum($sum, $arr[$i]);
}

echo $sum;