Regular expression for a language tag (as defined by BCP47)

Question

I need a regular expression for a language tag as defined by BCP 47.

I know that the full BNF syntax is available at http://www.rfc-editor.org/rfc/bcp/bcp47.txt and th

Answer 1

If using a CLDR-based function set, like PHP's intl extension, you can check if a locale exists in the intl database using a function like:

It takes about half a millisecond to load and search the data, so it won't be too much of a performance hit.

Of course, it will only find those in the database of the CLDR version supplied with the PHP version used, but will be updated with each subsequent PHP release.