public static function singleton()
    {
        $returnValue = null;

        
        
        if(is_null(self::$instance)){
        	$class = __CLASS__;				//used in case of subclassing
        	self::$instance = new $class();
        }
        $returnValue = self::$instance;
        
        

        return $returnValue;
    }
public static function singleton()
    {
        $returnValue = null;

        
        
        if(is_null(self::$instance)){
        	$class = __CLASS__;				//used in case of subclassing
        	self::$instance = new $class();
        }
        $returnValue = self::$instance;
        
        

        return $returnValue;
    }
public static function singleton ( ) { $ returnValue = null ; if ( is_null ( self :: $ instance ) ) { $ class = __CLASS__ ; //used in case of subclassing
 self :: $ instance = new $ class ( ) ; } $ returnValue = self :: $ instance ; return $ returnValue ; }
Main entry point to retrieve the unique NamespaceManager instance

@access public
@author Jerome Bogaerts, <jerome.bogaerts@tudor.lu>
@return common_ext_NamespaceManager
Main entry point to retrieve the unique NamespaceManager instance