> On Thu, Nov 6, 2014 at 3:39 PM, Kévin Dunglas <dung...@gmail.com> wrote: >> FILTER_VALIDATE_DOMAIN checks conformance with DNS RFCs : total length, >> label length and allowed characters (_ are allowed in domain names but many >> other characters are forbidden such as ~/+...). I'll add IDN support too >> when IDN support for streams will be merged. > > I am not trying to argue, but where does it say that ~/+ are > disallowed, yet an underscore is? The only rule *allowing* underscores > that I've seen is the one that says any binary string is a valid DNS > record value.
FWIW, there *is* a practical in-use (de facto if nothing else) convention of using _ in hosts for DKIM: $ dig +short -ttxt mandrill._domainkey.mailchimp.com "k=rsa\; p=MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQCrLHiExVd55zd/IQ/J/mRwSRMAocV/hMB3jXwaHH36d9NaVynQFYV8NaWi69c1veUtRzGt7yAioXqLj7Z4TeEUoOLgrKsn8YnckGs9i3B3tVFB+Ch/4mPhXWiNfNdynHWBcPcbJ8kjEQ2U8y78dHZj1YeRXXVvWob2OaKynO8/lQIDAQAB\;” S -- PHP Internals - PHP Runtime Development Mailing List To unsubscribe, visit: http://www.php.net/unsub.php
