Custom validation class for CNP field in Laravel

Cnp.php

<?php
/**
* @author Daniel Placinta
* http://artgames.ro
* Heavy inspiration from https://github.com/alceanicu/cnp/
*/
namespace App\Rules;

use Illuminate\Contracts\Validation\Rule;

class Cnp implements Rule
{
    private $_isValid = false;
    private $_cnp = [];
    private $_year = false;
    private $_month = false;
    private $_day = false;
    private $_cc = false;
    private $_serial = false;
    private static $controlKey = [2, 7, 9, 1, 4, 6, 3, 5, 8, 2, 7, 9];
    private static $countyCode = [
        '01' => 'Alba',
        '02' => 'Arad',
        '03' => 'Arges',
        '04' => 'Bacau',
        '05' => 'Bihor',
        '06' => 'Bistrita-Nasaud',
        '07' => 'Botosani',
        '08' => 'Brasov',
        '09' => 'Braila',
        '10' => 'Buzau',
        '11' => 'Caras-Severin',
        '12' => 'Cluj',
        '13' => 'Constanta',
        '14' => 'Covasna',
        '15' => 'Dambovita',
        '16' => 'Dolj',
        '17' => 'Galati',
        '18' => 'Gorj',
        '19' => 'Harghita',
        '20' => 'Hunedoara',
        '21' => 'Ialomita',
        '22' => 'Iasi',
        '23' => 'Ilfov',
        '24' => 'Maramures',
        '25' => 'Mehedinti',
        '26' => 'Mures',
        '27' => 'Neamt',
        '28' => 'Olt',
        '29' => 'Prahova',
        '30' => 'Satu Mare',
        '31' => 'Salaj',
        '32' => 'Sibiu',
        '33' => 'Suceava',
        '34' => 'Teleorman',
        '35' => 'Timis',
        '36' => 'Tulcea',
        '37' => 'Vaslui',
        '38' => 'Valcea',
        '39' => 'Vrancea',
        '40' => 'Bucuresti',
        '41' => 'Bucuresti S.1',
        '42' => 'Bucuresti S.2',
        '43' => 'Bucuresti S.3',
        '44' => 'Bucuresti S.4',
        '45' => 'Bucuresti S.5',
        '46' => 'Bucuresti S.6',
        '51' => 'Calarasi',
        '52' => 'Giurgiu'
    ];

    public function passes($attribute, $value)
    {
        $this->_cnp = str_split(trim($value));
        return $this->validateCnp();
    }

    public function message()
    {
        return ':input is not a valid CNP.';
    }

    /**
     * Validation for Romanian Social Security Number (CNP)
     * @return bool
     */
    private function validateCnp()
    {
        $cnpArray = $this->_cnp;
        // CNP must have 13 characters
        if (count($cnpArray) != 13) {
            return false;
        }
        // Set and check year, month, day and county
        if ($this->year() && $this->month() && $this->day() && $this->county()) {
            $hashArray = self::$controlKey;
            $hashSum = 0;
            // All characters must be numeric
            for ($i = 0; $i <= 12; $i++) {
                if (!is_numeric($cnpArray[$i])) {
                    return false;
                }
                if ($i < 12) {
                    $hashSum += (int)$cnpArray[$i] * (int)$hashArray[$i];
                }
            }
            $hashSum = $hashSum % 11;
            if ($hashSum == 10) {
                $hashSum = 1;
            }
            return ($cnpArray[12] == $hashSum);
        }
        return false;
    }

    private function year()
    {
        $cnp = $this->_cnp;
        $year = ($cnp[1] * 10) + $cnp[2];
        switch ($cnp[0]) {
            // romanian citizen born between 1900.01.01 and 1999.12.31
            case 1 :
            case 2 :
                $year += 1900;
                break;
            // romanian citizen born between 1800.01.01 and 1899.12.31
            case 3 :
            case 4 :
                $year += 1800;
                break;
            // romanian citizen born between 2000.01.01 and 2099.12.31
            case 5 :
            case 6 :
                $year += 2000;
                break;
            // residents && people with foreign citizenship
            case 7 :
            case 8 :
            case 9 :
                $year += 2000;
                if ($year > (int)date('Y') - 14) {
                    $year -= 100;
                }
                break;
            default :
                $year = 0;
                break;
        }
        $this->_year = $year;
        return ($year >= 1800) && ($year <= 2099);
    }

     /**
     * Check and set month
     * @return boolean
     */
    private function month()
    {
        $this->_month = (int)($this->_cnp[3] . $this->_cnp[4]);
        return ($this->_month >= 1) && ($this->_month <= 12);
    }
    /**
     * Check and set day
     * @return boolean
     */
    private function day()
    {
        $this->_day = (int)($this->_cnp[5] . $this->_cnp[6]);
        if (($this->_day < 1) || ($this->_day > 31)) {
            return false;
        }
        if ($this->_day > 28) {
            // validate date for day of month - 28, 29, 30 si 31
            if (checkdate($this->_month, $this->_day, $this->_year) === false) {
                return false;
            }
        }
        return true;
    }
    /**
     * Check and set county code
     * @return boolean
     */
    private function county()
    {
        $this->_cc = (string)($this->_cnp[7] . $this->_cnp[8]);
        return array_key_exists($this->_cc, self::$countyCode);
    }

        /**
     * Get Birth Place from Romanian Social Security Number (CNP)
     * @param string|bool $defaultReturn
     * @return string|bool
     */
    public function getBirthCountyFromCNP($defaultReturn = false)
    {
        if ($this->_isValid) {
            return self::$countyCode[$this->_cc];
        }
        return $defaultReturn;
    }
    /**
     * Get Birth Date from Romanian Social Security Number (CNP)
     * @param string $format
     * @return string|boolean
     */
    public function getBirthDateFromCNP($format = 'Y-m-d')
    {
        if ($this->_isValid) {
            return \DateTime::createFromFormat('Y-m-d', "{$this->_year}-{$this->_month}-{$this->_day}")->format($format);
        }
        return false;
    }
    /**
     * Get gender from Romanian Social Security Number (CNP)
     * @param string $m
     * @param string $f
     * @return string|boolean
     */
    public function getGenderFromCNP($m = 'M', $f = 'F')
    {
        if ($this->_isValid) {
            if (in_array($this->_cnp[0], [1, 3, 5, 7])) {
                return $m;
            } elseif (in_array($this->_cnp[0], [2, 4, 6, 8])) {
                return $f;
            }
        }
        return false;
    }
    /**
     * @return bool|string
     */
    public function getSerialNumberFromCNP()
    {
        if ($this->_isValid) {
            return $this->_cnp[9] . $this->_cnp[10] . $this->_cnp[11];
        }
        return false;
    }
}