Operace s binárními čísly PHP

<?php


class Binary
{

    public function prepareNumber($num, $length)
    {
        for ($i = $length - 1; $i >= 0; $i--)
        {
            $result[$i] = 0;
        }

        for ($i = strlen($num) - 1; $i >= 0; $i--)
        {
            $result[$i] = $num[$i];
        }

        return implode('', $result);
    }


    public function sum($num1, $num2, $length = 8)
    {
        for ($i = $length - 1; $i >= 0; $i--)
        {
            $result[$i] = 0;
        }

        for ($i = $length - 1; $i >= 0; $i--)
        {
            $result[$i] = $num1[$i] + $num2[$i] + $result[$i];

            if ($result[$i] > 1)
            {
                $result[$i] = $result[$i] == 2 ? 0 : 1;
                $result[$i-1] = 1;
            }
        }

        return $result;
    }


    public function sub($num1, $num2, $length = 8)
    {
        return $this->sum($num1, $this->negate($num2));
    }




    public function negate($num)
    {
        $length = strlen($num) - 1;
        for ($i = $length; $i >= 0; $i--)
            $num[$i] = $num[$i] == 1 ? 0 : 1;

        return implode('', $this->sum($num, $this->prepareNumber('1', $length + 1)));
    }

    public function check($num1, $num2)
    {
        $num1 = intval($num1);
        $num2 = intval($num2);
        if ($num1 > $num2)
            return -1;
        else if ($num1 < $num)
            return 1;
        else
            return 0;
    }


}

$bin = new Binary();


$input_1 = $bin->prepareNumber('11', 8);
$input_2 = $bin->prepareNumber('1', 8);

$number = $bin->sum($input_1, $input_2);

for ($i = 0; $i < sizeof($number); $i++)
{
    echo($number[$i]);
}

echo('<p>');

$number = $bin->sub($input_1, $input_2);

for ($i = 0; $i < sizeof($number); $i++)
{
    echo($number[$i]);
}

echo('<p>');

echo($bin->check($input_1, $input_2));

?>