PerfectNumber.php

<?php

/**
This function returns true
* if the submitted number is perfect,
* false if it is not.
*
* A perfect number is a positive integer that is
* equal to the sum of its positive proper
* divisors, excluding the number itself.
*
* About perfect numbers: https://en.wikipedia.org/wiki/Perfect_number
*
* @author Marco https://github.com/MaarcooC
* @param int $number
* @return bool
*/
function perfect_number($number)
{
    /*Input validation*/
    if (!is_int($number) || $number <= 1) {
        /*Return false for non-integer or non-positive numbers*/
        return false;
    }

    $divisorsSum = 1; /*1 is a common divisor for every number*/

    /*Check for divisors up to the square root of the number*/
    for ($i = 2; $i * $i <= $number; $i++) {
        if ($number % $i == 0) {
            $divisorsSum += $i; /*add i to the sum of divisors*/
            if ($i != $number / $i) { /*add the complement divisor*/
                $divisorsSum += $number / $i;
            }
        }
    }

    return $divisorsSum == $number;
}