src/Module/SQLModule.php
static public function init($args = '')
    {
        $called_class_name = get_called_class();
        if (empty(self::$instance[$called_class_name])) {
            self::$instance[$called_class_name] = new $called_class_name($args);
        }

        return self::$instance[$called_class_name];
    }
static public function init($args = '')
    {
        $called_class_name = get_called_class();
        if (empty(self::$instance[$called_class_name])) {
            self::$instance[$called_class_name] = new $called_class_name($args);
        }

        return self::$instance[$called_class_name];
    }
实例化当前类的子类

@param string $args
@return static::get_called_class()