/**
  * @access private
  * @since  1.0
  * @static
  *
  * @return ezTOC
  */
 public static function instance()
 {
     if (!isset(self::$instance) && !self::$instance instanceof ezTOC) {
         self::$instance = new ezTOC();
         self::defineConstants();
         self::includes();
         self::hooks();
     }
 }