/** * Main Footnotes_Propelled Instance * * Ensures only one instance of Footnotes_Propelled is loaded or can be loaded. * * @since 1.0.0 * @static * @see Footnotes_Propelled() * @return Main Footnotes_Propelled instance */ public static function instance($file = '', $version = '1.0.0') { if (is_null(self::$_instance)) { self::$_instance = new self($file, $version); } return self::$_instance; }