25     public static function get($sClassName)
 
   27         $sClassName = strtolower($sClassName);
 
   28         if (isset(self::$_aInstances[$sClassName])) {
 
   29             return self::$_aInstances[$sClassName];
 
   31             self::$_aInstances[$sClassName] = 
oxNew($sClassName);
 
   33             return self::$_aInstances[$sClassName];
 
   47     public static function set($sClassName, $oInstance)
 
   49         $sClassName = strtolower($sClassName);
 
   51         if (is_null($oInstance)) {
 
   52             unset(self::$_aInstances[$sClassName]);
 
   57         self::$_aInstances[$sClassName] = $oInstance;
 
  115         return array_keys(self::$_aInstances);