/**
  * gets the HTTP content type charset for the current request.
  * returns false for non-text content types.
  *
  * Note: getHTTPBody must be called before this.
  *
  * @return string the HTTP content type charset for the current request.
  * @access private
  */
 function getHTTPContentTypeCharset()
 {
     if (count($this->requestAttachments) > 0) {
         return false;
     }
     return parent::getHTTPContentTypeCharset();
 }