Vergi kimlik numarası doğrulama

TaxNumber.php

<?php

namespace Libraries;

class TaxNumber
{
    public static function check($tax)
    {
        $tax = str_replace(' ', '', trim($tax));
        if (strlen($tax) != 10) {
            return false;
        }
        $sum = 0;
        for ($i=0; $i < 9; $i++) {
            $val = ($tax[$i] + (9 - $i)) % 10;
            $val2 = ($val * (2 ** (9 - $i))) % 9;
            if ($val != 0 && $val2 == 0) {
                $val2 = 9;
            }
            $sum += $val2;
        }
        $last = (10 - ($sum % 10)) % 10;
        if ($last != $tax[9]) {
            return false;
        }
        return true;
    }
}