24     public static function get( $sClassName )
 
   26         $sClassName = strtolower( $sClassName );
 
   27         if ( isset( self::$_aInstances[$sClassName] ) ) {
 
   28             return self::$_aInstances[$sClassName];
 
   30             self::$_aInstances[$sClassName] = 
oxNew( $sClassName );
 
   31             return self::$_aInstances[$sClassName];
 
   45     public static function set( $sClassName, $oInstance )
 
   47         $sClassName = strtolower( $sClassName );
 
   49         if ( is_null( $oInstance ) ) {
 
   50             unset( self::$_aInstances[$sClassName] );
 
   54         self::$_aInstances[$sClassName] = $oInstance;
 
  112         return array_keys( self::$_aInstances );