string ingres_charset ( resource $link )
ingres_charset() is called to determine the character set being used by the Ingres client, from II_CHARSETxx (where xx is the installation code). Note: You can override the value returned by using the function putenv(). Changing the value of II_CHARSETxx in a running Ingres installation can cause data corruption.
Returns a string with the value for II_CHARSETxx or returns NULL if the value could not be determined.