idn_to_ascii('faß.de');will return fass.de(Due to Germans using the ß symbol as a contraction of ss)idn_to_ascii('faß.de', IDNA_NONTRANSITIONAL_TO_ASCII);will return xn--fa-hia.de(This is the correct behavior too allow faß.de and fass.de to be registered as different domain names.)idn_to_utf8('xn--fa-hia.de');will return fass.deidn_to_utf8('xn--fa-hia.de', IDNA_NONTRANSITIONAL_TO_UNICODE);will return faß.de(Again this is the correct behavior.)