Problem Validate NIE

[gremin]

We encountered some trouble to validate NIE. The problem come from replace Y, X and Z with 1, 0 and 2. With the current code, when the NIE ends by Z we replace it by 2 to call isValidNIF(). Next, this method calls getNIFCheckDigit() which return Z. Unfortunately, the last char at this moment is 2...

I propose this code for method isValidNIE() :

function isValidNIE($docNumber) {
    $isValid = false;
    $fixedDocNumber = "";
    if (!preg_match("/^[A-Z]+$/i", substr($fixedDocNumber, 1, 1))) {
        $fixedDocNumber = strtoupper(substr("000000000" . $docNumber, - 9));
    } else {
        $fixedDocNumber = strtoupper($docNumber);
    }
    if (isValidNIEFormat($fixedDocNumber)) {
        if (substr($fixedDocNumber, 1, 1) == "T") {
            $isValid = true;
        } else {
            $writtenDigit = substr($fixedDocNumber, - 1, 1);

            /* The algorithm for validating the check digits of a NIE number is
            identical to the altorithm for validating NIF numbers. We only have to
            replace Y, X and Z with 1, 0 and 2 respectively; and then, run
            the NIF altorithm */
            $fixedDocNumber = str_replace('Y', '1', $fixedDocNumber);
            $fixedDocNumber = str_replace('X', '0', $fixedDocNumber);
            $fixedDocNumber = str_replace('Z', '2', $fixedDocNumber);

            $writtenDigit2 = substr($fixedDocNumber, - 1, 1);

            $correctDigit = getNIFCheckDigit($fixedDocNumber);
            if ($writtenDigit == $correctDigit || $writtenDigit2 == $correctDigit) {
                $isValid = true;
            }
        }
    }

    return $isValid;
}