public function getRegistrableDomain()
    {
        if (null === $this->suffix) {
            return null;
        }

        return null === $this->hostname ? null : $this->hostname . '.' . $this->suffix;
    }
public function getRegistrableDomain()
    {
        if (null === $this->suffix) {
            return null;
        }

        return null === $this->hostname ? null : $this->hostname . '.' . $this->suffix;
    }
public function getRegistrableDomain ( ) { if ( null === $ this -> suffix ) { return null ; } return null === $ this -> hostname ? null : $ this -> hostname . '.' . $ this -> suffix ; }
Returns registrable domain or null.

@return null|string
Returns registrable domain or null .