/**
* Returns true if and only if $value follows the Luhn algorithm (mod-10 checksum)
*
* @param string $value
* @return boolean
*/
public function isValid($value)
{
$this->_setValue($value);
if (!is_string($value)) {
$this->_error(self::INVALID, $value);
return false;
}
if (!ctype_digit($value)) {
$this->_error(self::CONTENT, $value);
return false;
}
$length = strlen($value);
$types = $this->getType();
$foundp = false;
$foundl = false;
foreach ($types as $type) {
foreach ($this->_cardType[$type] as $prefix) {
if (substr($value, 0, strlen($prefix)) == $prefix) {
$foundp = true;
if (in_array($length, $this->_cardLength[$type])) {
$foundl = true;
break 2;
}
}
}
}
if ($foundp == false){
$this->_error(self::PREFIX, $value);
return false;
}
if ($foundl == false) {
$this->_error(self::LENGTH, $value);
return false;
}
$sum = 0;
$weight = 2;
for ($i = $length - 2; $i >= 0; $i--) {
$digit = $weight * $value[$i];
$sum += floor($digit / 10) + $digit % 10;
$weight = $weight % 2 + 1;
}
if ((10 - $sum % 10) % 10 != $value[$length - 1]) {
$this->_error(self::CHECKSUM, $value);
return false;
}
if (!empty($this->_service)) {
try {
$callback = new Callback($this->_service);
$callback->setOptions($this->_type);
if (!$callback->isValid($value)) {
$this->_error(self::SERVICE, $value);
return false;
}
} catch (\Exception $e) {
$this->_error(self::SERVICEFAILURE, $value);
return false;
}
}
return true;
}
