problem21.php

<?php
/*Let d(n) be defined as the sum of proper divisors of n (numbers less than n which divide evenly into n).
If d(a) = b and d(b) = a, where a ≠ b, then a and b are an amicable pair and each of a and b are called amicable numbers.

For example, the proper divisors of 220 are 1, 2, 4, 5, 10, 11, 20, 22, 44, 55 and 110; therefore d(220) = 284. The proper
divisors of 284 are 1, 2, 4, 71 and 142; so d(284) = 220.

Evaluate the sum of all the amicable numbers under 10000.
*/
function sumOfDivisors($n){
    for($x = 1; $x<$n; $x++){
        if($n % $x === 0){
            $array[] = $x;
        }
    }
    print_r($array);
    $sum = 0;
    foreach($array as $value){
        $sum += $value;
    }
    echo 'sum is ' + $sum;
}

sumOfDivisors(10000);

//sum is 14211

?>