How to check if a given number is a perfect number.

<?php
function isPerfectNumber($number) {
    $sum = 1;

    for ($i = 2; $i <= sqrt($number); $i++) {
        if ($number % $i === 0) {
            $sum += $i;

            // If the divisors are equal, only count once (e.g., for perfect squares)
            if ($i !== $number / $i) {
                $sum += $number / $i;
            }
        }
    }

    return $sum === $number;
}

$testNumber = 28;

if (isPerfectNumber($testNumber)) {
    echo "$testNumber is a perfect number.";
} else {
    echo "$testNumber is not a perfect number.";
}
?>

• The script defines a function isPerfectNumber that checks whether a given number is a perfect number.
• A perfect number is a positive integer that is equal to the sum of its proper divisors (excluding itself).
• The function iterates through divisors up to the square root of the number, adding them to the sum.
• The script then calls the function with a sample number ($testNumber) and prints the result.