laravel 中一段关于闭包的代码

public function share(Closure $closure)
    {
        return function ($container) use ($closure) {
            // We'll simply declare a static variable within the Closures and if it has
            // not been set we will execute the given Closures to resolve this value
            // and return it back to these consumers of the method as an instance.
            static $object;

            if (is_null($object)) {
                $object = $closure($container);
            }

            return $object;
        };
    }

这段代码中 static 有什么意义