A simple validation for companies national number (تایید صحت شناسه ملی به زبان پی اچ پی)

Iranian National Number (for companies) Validation

public function checkShenaseMelli($shenase)
    {
        if (strlen($shenase) != 11)
            return false;
        if (intval(substr($shenase, 3, 6)) == 0)
            return false;
        $c = intval(substr($shenase, 10, 1));
        $d = intval(substr($shenase, 9, 1)) + 2;
        $z = array(29, 27, 23, 19, 17);
        $s = 0;
        for ($i = 0; $i < 10; $i++) {
            $s += ($d + intval(substr($shenase, $i, 1))) * $z[$i % 5];
        }
        $s = $s % 11;
        if ($s == 10)
            $s = 0;
        return $c == $s;
    }