/**
* Validate an ISBN value
*
* @param string $isbn Number to validate
* @param string $ver Version to validate against
*
* @return integer|false Returns the Version to signal validity or false if
* ISBN number is not valid
*
* @access private
*/
function _isIsbnValid($isbn, $ver = ISBN_DEFAULT_INPUTVERSION)
{
/* version handling */
$r = ISBN::_isbnVersionIs($ver);
if ($r === false) {
return false;
}
if ($ver === ISBN_VERSION_UNKNOWN) {
$ver = ISBN::_isbnVersionGuess($isbn);
}
if (ISBN::_isbnVersionIsValid($ver) === false) {
return false;
}
/* since a version is available now, normalise the ISBN input */
$isbnn = ISBN::_normaliseISBN($isbn);
if ($isbnn === false) {
return false;
}
/* normalzied ISBN and Version available, it's ok now
* to perform indepth checks per version */
switch ($ver) {
case ISBN_VERSION_ISBN_10:
/* check syntax against checkdigit */
$isbnbody = ISBN::_extractISBNBody($isbnn);
$check = ISBN::_extractCheckdigit($isbnn);
if ($check === false) {
return false;
}
$checkdigit = ISBN::_checkdigitISBN10($isbnbody);
if ($checkdigit === false) {
return false;
}
if ($checkdigit !== $check) {
return false;
}
/* check registrationgroup validity */
$registrationgroup = false;
$subbody = false;
$r = ISBN::_isbnBodyParts($isbnbody, $registrationgroup, $subbody);
if ($r == false) {
return false;
}
/* check for undefined registrationgroup */
if (strlen($registrationgroup) == 0) {
return false;
}
/* check registrant validity */
$groupid = intval($registrationgroup);
$registrant = false;
$publication = false;
$r = ISBN::_isbnSubbodyParts($subbody, $groupid, $registrant, $publication);
if ($r == false) {
return false;
}
return true;
case ISBN_VERSION_ISBN_13:
case ISBN_VERSION_ISBN_13_978:
/* validate EAN Prefix */
$ean = ISBN::_extractEANPrefix($isbnn);
if ($ean !== '978') {
return false;
}
/* check syntax against checkdigit */
$isbnbody = ISBN::_extractISBNBody($isbnn);
$check = ISBN::_extractCheckdigit($isbnn);
if ($check === false) {
return false;
}
$checkdigit = ISBN::_checkdigitISBN13($isbnbody);
if ($checkdigit === false) {
return false;
}
if ($check !== $checkdigit) {
return false;
}
/* validate group */
$isbnbody = ISBN::_extractISBNBody($isbnn);
if ($isbnbody === false) {
return false;
}
$registrationgroup = false;
$subbody = false;
$r = ISBN::_isbnBodyParts($isbnbody, $registrationgroup, $subbody);
if ($r === false) {
return false;
}
/* check for undefined registrationgroup */
if (strlen($registrationgroup) == 0) {
return false;
}
/* validate publisher */
$registrant = false;
$publication = false;
$r = ISBN::_isbnSubbodyParts($subbody, $registrationgroup, $registrant, $publication);
if ($r === false) {
return false;
}
return $ver;
case ISBN_VERSION_ISBN_13_979:
/* not yet standarized */
return false;
}
return false;
}
