I'm very interested what differences microptimizations (like using while(list() = each()) instead of foreach) make when scaling.

Also, I noticed that when I clicked the return to website after clicking on the subscribe button your website, it went to google.com instead, and when I clicked continue to our website button after clicking the email confirmation link, it went to http://www.phpscalingbook.com/ (404 error).

And if you need any proofreaders, I'd be more than happy to help!