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.