protected function isAbstract($middleware): bool
    {
        return is_string($middleware) &&
            class_exists($middleware) &&
            is_a($middleware, MiddlewareInterface::class, true);
    }
protected function isAbstract($middleware): bool
    {
        return is_string($middleware) &&
            class_exists($middleware) &&
            is_a($middleware, MiddlewareInterface::class, true);
    }
protected function isAbstract ( $ middleware ) : bool { return is_string ( $ middleware ) && class_exists ( $ middleware ) && is_a ( $ middleware , MiddlewareInterface :: class , true ) ; }
Determines if the given middleware value is a string that can be instantiated.
Note that it does not check an application container.

@param mixed $middleware
@return bool
Determines if the given middleware value is a string that can be instantiated . Note that it does not check an application container .