add some code(32bit) like follow :
public function network()
{
return long2ip(ip2long($this->address) & ip2long($this->netmask()));
}
public function broadcast()
{
return long2ip(ip2long($this->network()) | (~(ip2long($this->netmask()))));
}
public function inverse()
{
return long2ip(~(ip2long('255.255.255.255') << (32 - $this->netbits)));
}