@nikic would it make sense to take this approach? or are y'all considering dropping the PHP5 content?

I don't think we will drop PHP 5 content, but have it clearly separated from PHP 7 (and future PHP 8) is a good thing IMO.

My only concern here would be that the content is duplicated on two pages, rather one redirecting to the other. Do you know whether rst/sphinx also supports redirects (via JS probably?)

I did some research on the redirect and it is doable with JS. There doesn't seem to be something baked into sphinx to do it. https://tech.signavio.com/2017/managing-sphinx-redirects

How painful would it be to just break those links? Is it fair to say that most people are now interested in PHP7? Would a 404 explaining the move be enough?

Since I'm illiterate in python I wrote something in PHP to handle the redirects, it generates static files. Not exactly elegant, but I think it makes sense to have this as part of the "build" process and not part of the actual book.

@jpauli @nikic what do you think of this?

Looks like a reasonable approach to me. Someone will have to push a new build with this (unfortunately not automated...)

Better late than never ... merged and pushed a new build. Redirects working great. Thanks for doing this!