public static function getInstance() { if (!self::$_instance) { self::$_instance = new self(); } return self::$_instance; }
protected static function _get_instance($class = '') { return isset(self::$_instance) ? self::$_instance : (self::$_instance = new $class()); }
static function get_instance($params = null) { return isset(self::$_instance) ? self::$_instance : (self::$_instance = new static($params)); }