Day 19: Interfaces

https://www.hackerrank.com/challenges/30-interfaces/problem

<?php
interface AdvancedArithmetic{
    public function divisorSum($n);
}

/*
 * Write your code here
 */
class Calculator implements AdvancedArithmetic {
    function divisorSum($n) {
        $result = 0;
        for($i=1;$i<=$n;$i++){
            if($n%$i == 0){
                $result += $i;
            }
        }
        return $result;
    }
}

$n=intval(fgets(STDIN));
$myCalculator=new Calculator();
if($myCalculator instanceof AdvancedArithmetic)//checking if Calculator has implemented AdvancedArithemtic
{
    $sum=$myCalculator->divisorSum($n);
    echo "I implemented: AdvancedArithmetic\n".$sum;
}
else
{
    echo "Wrong answer";// You will get this output if you dont implement
}
?>