I was unable to find anywhere a Portuguese national postal service, package registry number check-digit validation. So, I politely asked them and soon after a PDF describing the algorithm was on my desk.
It’s pretty simple and standard stuff (only an awkward multiplier order of each digit), so the best way to describe it’s with a validation function in PHP (even for non PHP users/programmers should be simple to enough to understand at a glance):
01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 | function checkDigitCTT($ref) { if (! preg_match('/^[a-z]{2}[0-9]{9}[a-z]{2}$/i', $ref)) return false; $digits = substr($ref, 2, 9); $multipliers = array(8,6,4,2,3,5,9,7); $tmp = 0; foreach ($multipliers as $k => $v) $tmp = $tmp + (((int) $digits[$k]) * $v); $tmp = round($tmp % 11); if ($tmp == 0) $check_digit = 5; else if ($tmp == 1) $check_digit = 0; else $check_digit = 11 - $tmp; if ($check_digit == ((int) $digits[8])) return true; return false;} |