升级到Laravel 5.3后，您需要重新保存视图以使$ loop变量生效，因为您可能正在查看缓存版本.我遇到了同样的问题，升级了，仍然有问题，重新保存了视图(修改后)，然后$ loop起作用了.

After upgrading to Laravel 5.3, you'll need to re-save your views in order to see the $loop variable take effect as you may be viewing the cached versions. I had the same issue, upgraded, still had the issue, re-saved the view (after modifying) and then $loop worked.