original_string: public static function isValidISBN10($isbn)
      {
          $isbn = self::normalizeISBN($isbn);
          if (strlen($isbn) != 10) {
              return false;
          }
          return substr($isbn, 9) == self::getISBN10CheckDigit(substr($isbn, 0, 9));
      }
code: public static function isValidISBN10($isbn)
      {
          $isbn = self::normalizeISBN($isbn);
          if (strlen($isbn) != 10) {
              return false;
          }
          return substr($isbn, 9) == self::getISBN10CheckDigit(substr($isbn, 0, 9));
      }
code_tokens: public static function isValidISBN10 ( $ isbn ) { $ isbn = self :: normalizeISBN ( $ isbn ) ; if ( strlen ( $ isbn ) != 10 ) { return false ; } return substr ( $ isbn , 9 ) == self :: getISBN10CheckDigit ( substr ( $ isbn , 0 , 9 ) ) ; }
docstring: Is the provided ISBN-10 valid?
  
  @param string $isbn The ISBN-10 to test.
  
  @return boolean
docstring_tokens: Is the provided ISBN - 10 valid?