He's not making that argument!
From the article: "You can learn PHP in a day or two if you're familiar with any other language. You can write PHP code in any editor or environment you want. Emacs? Vim? Notepad? nano? Who cares? Whatever floats your boat. Being a stupid language also means that everyone knows it. "
The author didn't spend a lot of time talking about learning PHP because there's not much to learn. There's nothing surprising in the components in the PHP stack. If you know HTML, adding PHP has low overhead. DB reads and writes are simple. If you can program in another language, you know all of the logic statements you need to write an application. If you need an example, there are probably tens of thousands of bad PHP tutorials online with bad sample code that still manages to work.
I've learned PHP and Common Lisp from scratch at different points in my life, and PHP had a much lower barrier to entry. I installed and configured PHP on my local machine and made a stats-tracking webpage all on the same day. This was my first server-side web application ever, plus my first database program ever.
Fast forward 4 years, and I worked through "ANSI Common Lisp" for a month before I felt comfortable writing regular applications in Lisp. Then I installed Hunchentoot and stumbled around for a while, but was able to figure out how to generate static content. Most of the Hunchentoot tutorials online were for older versions, but I found one that proved invaluable. I then ended up patching S-XML, because it was only written to support 5 or 6 of the 250+ "&" style HTML character codes. I sent that patch to the mailing list, but I bet nobody ever got it. I tried to hook up a database, and found Postmodern, which was nice. Thank God I already knew Emacs, but I wasted more than a day fighting with upgrading SLIME and SBCL at the same time.
The Common Lisp path doesn't sound so bad, but compare it to my PHP experience - I wrote an application on the same day I first looked at PHP. By the time I was integrating Database code, I was well over a month into learning Common Lisp.