Negotiate the client's preferred language.
-> ***NOTE:*** The first elemement of $supported languages serves as a default if no language matches.
+> **Note:** The first elemement of $supported languages serves as a default if no language matches.
## Params:
-* ```array $supported```
+* array $supported
List of supported content languages.
-* Optional reference ```array &$result```
+* Optional reference array &$result
Out parameter recording negotiation results.
## Returns:
-* ```NULL```, if negotiation fails.
-* ```string```, the negotiated language.
+* NULL, if negotiation fails.
+* string, the negotiated language.