Product.php

<?php


class Product implements ArrayAccess
{

    private $number;

    /**
     * Product constructor.
     * @param int $number
     */
    public function __construct(int $number)
    {
        $this->number = str_split(decbin($number));

    }

    /**
     * @param mixed $offset
     * @return bool
     */
    public function offsetExists($offset)
    {
        return isset($this->number[$offset]);
    }

    /**
     * @param mixed $offset
     * @return mixed|null
     */
    public function offsetGet($offset)
    {
        return isset($this->number[$offset]) ? $this->number[$offset] : null;
    }


    /**
     * @param mixed $offset
     * @param mixed $value
     * @throws Exception
     */
    public function offsetSet($offset,  $value)
    {

        if ($value === 0 || $value === 1) {

            if (is_null($offset)) {
                $this->number[] = $value;
            } else {
                $this->number[$offset] = $value;
            }
        }else{
            throw new Exception('Podaj 0 lub 1');
        }
    }


    /**
     * @param mixed $offset
     */
    public function offsetUnset($offset)
    {
        unset($this->number[$offset]);
    }


    /**
     * @return int
     */
    public function getInt() : int
    {
         return implode("", $this->number);
    }

}

$number = new Product(15);
$number->offsetSet(1, 1);
$number->offsetGet(2);