function IsbnValidator::validateIsbn10

1 call to IsbnValidator::validateIsbn10()

IsbnValidator::validate in vendor/symfony/validator/Constraints/IsbnValidator.php

Checks if the passed value is valid.

File

vendor/symfony/validator/Constraints/IsbnValidator.php, line 95

Class

IsbnValidator

Validates whether the value is a valid ISBN-10 or ISBN-13.

Namespace

Symfony\Component\Validator\Constraints

Code

protected function validateIsbn10(string $isbn) : string|bool {
    // Choose an algorithm so that ERROR_INVALID_CHARACTERS is preferred
    // over ERROR_TOO_SHORT/ERROR_TOO_LONG
    // Otherwise "0-45122-5244" passes, but "0-45122_5244" reports
    // "too long"
    // Error priority:
    // 1. ERROR_INVALID_CHARACTERS
    // 2. ERROR_TOO_SHORT/ERROR_TOO_LONG
    // 3. ERROR_CHECKSUM_FAILED
    $checkSum = 0;
    for ($i = 0; $i < 10; ++$i) {
        // If we test the length before the loop, we get an ERROR_TOO_SHORT
        // when actually an ERROR_INVALID_CHARACTERS is wanted, e.g. for
        // "0-45122_5244" (typo)
        if (!isset($isbn[$i])) {
            return Isbn::TOO_SHORT_ERROR;
        }
        if ('X' === $isbn[$i]) {
            $digit = 10;
        }
        elseif (ctype_digit($isbn[$i])) {
            $digit = $isbn[$i];
        }
        else {
            return Isbn::INVALID_CHARACTERS_ERROR;
        }
        $checkSum += $digit * (10 - $i);
    }
    if (isset($isbn[$i])) {
        return Isbn::TOO_LONG_ERROR;
    }
    return 0 === $checkSum % 11 ? true : Isbn::CHECKSUM_FAILED_ERROR;
}