File Content: Isbn10.php <?php namespace Laminas\Validator\Isbn; /** * @deprecated Since 2.61.0 - This class will be inlined in v3.0 * * @final */ class Isbn10 { /** * @param string $value * @return int|string */ public function getChecksum($value) { $sum = $this->sum($value); return $this->checksum($sum); } /** * Calculate the value sum. * * @param string $value * @return int */ private function sum($value) { $sum = 0; for ($i = 0; $i < 9; $i++) { $sum += (10 - $i) * (int) $value[$i]; } return $sum; } /** * Calculate the checksum for the value's sum. * * @param int $sum * @return int|string */ private function checksum($sum) { $checksum = 11 - ($sum % 11); if ($checksum === 11) { return '0'; } if ($checksum === 10) { return 'X'; } return $checksum; } } Submit