rc.php

        // Kontrola rodného čísla.
        // @author: Marián Černý
        private function is_RC_valid($value) {
                if (!preg_match('@^([0-9][0-9])([0-9][0-9])([0-9][0-9])/?([0-9]{3})([0-9])?$@', $value, $regs))
                        return false;

                list($expression, $year, $month, $day, $ext) = $regs;
                $c = isset($regs[5]) ? $regs[5] : "";

                if (strlen($value) == 9) {
                        if ($year >= 54)
                                // Nemame kontrolnu cislicu a rok je 54+.
                                return false;

                        $year += 1900;
                } else {
                        // If we used 10 digits RC number, we would have to use bcmod()
                        // instead of the modulo operator (%), because the RC number is
                        // out of range of integer on 32 bit systems.
                        $mod = "$year$month$day$ext" % 11;

                        if ($mod == 10)
                                $mod = 0;

                        if ($mod != $c)
                                // Nesedi kontrolna cislica.
                                return false;

                        if ($year < 54)
                                $year += 2000;
                        else
                                $year += 1900;
                }

                // K mesiacu je pripocitane 50 ak ide o zenu.
                // Od roku 2004 moze byt pripocitane 20 (muz) alebo 70 (zena).
                if ($month > 70 && $year >= 2004)
                        $month -= 70;
                else if ($month > 50)
                        $month -= 50;
                else if ($month > 20 && $year > 2003)
                        $month -= 20;

                // Cudzinci maju k dnu pripocitane 50.
                if ($day > 50 && $year >= 1954)
                        $day -= 50;

                if (!checkdate($month, $day, $year))
                        // Datum nedava zmysel.
                        return false;

                return true;
        }