Judging from these edits I made (listed below), removing "docs" from the URL fixes the link. For example, http://docs.php.net/book.mysql becomes https://www.php.net/book.mysql.
There are thousands more posts, likely more across the network. Can the URL be rewritten automatically? I would also suggest changing them to HTTPS.
I did not check too many posts to see if there were times this didn't fix the link, but it's certainly not possible to make them more broken than they are now.