How to install captcha (preferably 2 versions of Google) between the server (sites) and the user?

Question

PHP

How to install captcha (preferably 2 versions of Google) between the server (sites) and the user?
that is, when entering the site, it would automatically check who it is and either give the page or just a page with Google captcha appear (preferably version 2, since the 3rd one seems to be full of holes and the first one is outdated) and when it was passed, the site opened correctly and then everything worked, then if Google, at the next opening of the page on the site, still thought again that the bot would again be given out -)
who knows how to do this between the site, but rather all the server sites, and those who come in, no matter who he is _))))
And where do in ngix or what? tell me who knows.

Answer 1

What is the difficulty? You attach a captcha to your site, set it up so that, for example, without a session cookie, which the site issues only to those who have passed the captcha, the content is not returned, you drive people in the web server without cookies to the authorization page.

Answer 2

Most likely, this will not succeed, because. Google captcha token is tied to a specific domain.
Easier - restrict access to all unregistered, except for the list of ip-addresses / subnets of search bots.