/**
  * Set logger object. 
  *
  * The object should have a method "log" that accepts a value as 1st argument and
  * an optional string label as the 2nd.
  *
  * @param mixed $obj or a "falsey" value to disable
  * @return null
  */
 public static function setLogger($obj = null)
 {
     self::$_logger = $obj ? $obj : null;
 }