static string http\Env::negotiateCharset(array $supported[, array &$result)
Negotiate the client’s preferred character set.
NOTE:
The first elemement of $supported character sets serves as a default if no character set matches.
Params:
- array $supported
List of supported content character sets.
- Optional reference array &$result
Out parameter recording negotiation results.
Returns:
- NULL, if negotiation fails.
- string, the negotiated character set.