Hungarian tax number generator

HungarianTaxNumberGenerator.php

<?php

namespace Acme\Utilities;

use \DateTime;

class HungarianTaxNumberGenerator
{
    protected $number = '8';

    protected $birthDate;

    protected $baseDate = '1867-01-01';

    protected $random;

    public function __construct($birthDate, $random = null)
    {
        $this->birthDate = $birthDate;

        if ( ! is_null($random)) {
            $this->random = $random;
        } else {
            $this->random = $this->getRandom();
        }
    }

    public function generate()
    {
        $this->number .= $this->getDateDiff();
        $this->number .= $this->random;
        $this->number .= $this->calcLastDigit();

        return substr($this->number, 0, 10);
    }

    protected function getDateDiff()
    {
        try {
            $baseDate  = new DateTime($this->baseDate);
            $birthDate = new DateTime($this->birthDate);
        } catch (Exception $e) {
            echo $e->getMessage();

            return false;
        }

        return $birthDate->diff($baseDate)->format("%a");
    }

    public function getRandom()
    {
        return str_pad(mt_rand(0, 999), 3, '0', STR_PAD_LEFT);
    }

    protected function calcLastDigit()
    {
        $multiplications = [];

        for ($i = 0; $i < strlen($this->number); $i ++) {
            $multiplications[] = (int)$this->number[$i] * ($i + 1);
        }
        
        return array_sum($multiplications) % 11;
    }
}

// $generator = new HungarianTaxNumberGenerator('1970-09-11');
// echo $generator->generate();