How to differentiate access rights and give files from the file storage?

Question

PHP

Hello, there is an application in PHP as well as Nextcloud file storage, they work with each other via WebDAV.
The question is how to implement a file access check?

1. Do it using PHP, check access, download the file via webdav, and then give it to the user?

If it will be necessary to display a preview of several photos, will they first have to be downloaded via php and returned to the page? This is probably not productive, because the browser cache will not be used to the full extent, as if the path to the file were direct. Is it so?

2. Refine / use internal Nextcloud access role solutions? To use direct links.
3. What is the implementation in yandex, google services, how do they work with their file storages, access?

It is not possible to use external cloud solutions.

Answer 1

It's not very clear - why does your Nextcloud application work via WebDAV?

What is the implementation in yandex, google services, how do they work with their file storages, access?

Modern applications typically use object storage (S3 compatible).

It is not possible to use external cloud solutions.

If you want to host yourself, you can use MinIO. You can put it on the same host as the application, or you can deploy a system from several hosts.
If you stay with Nextcloud, then another option is to configure Nextcloud so that it can give files directly, without WebDAV, via a link, but there may be questions about authentication.

how to implement file access check?

It's not very clear - what is "access check"?