php regexp for national domains

Question

Thare are new nations domains and TLDs like "http://президент.рф/" - for Russian Federation domains, or http://example.新加坡 for Singapore...

Is there a regex to validate these domains?

I have found this one: What is the best regular expression to check if a string is a valid URL?

But when I try to use one of the expressions listed there - PHP is getting overhitted :)

preg_match(): Compilation failed: character value in \x{...} sequence is too large at offset 81

P.S.

1) Last part was solved by @OmnipotentEntity

2) But the main problem - to validate international domain - still exists, because example regexp doesn't validate well.

Answer 1

No, there's no regexp to validate those domains. Each TLD has different rules about which Unicode code points are permissible within their IDNs (if any). You would need a very big lookup table which would have to be kept up-to-date to know which specific characters are legal.

Furthermore there are rules about whether left-to-right written characters and right-to-left characters can be combined within a single DNS label.

BTW, the RFCs mentioned in the other comments are obsolete. The recently approved set are RFCs 5890 - 5895.

Answer 2

Use the "u" modifier to match unicode characters. The example you gave only uses the "i" modifier.