Exist/Work If-Modified-Since

As the title suggests, it exists / works If-Modified-Since in cwp?
It can work in digitalocean?

Hi, what do you mean?

If I set this on my pages.

header('If-Modified-Since: '.gmdate('D, d M Y H:i:s', $last_mod_header).' GMT');

The search engines see it?

I read that the server must be configured to allow search engines to access the value of the If-Modified-Since. CWP is configured?

I also read that some vps not allow us access to the If-Modified-Since, the combination digitalocean cwp, allows access?