Yes, the author reads the reviews here. That's me. The error in which a few quotes were replaced with underscores occurred during the publishing process, after I was finished with the book. I didn't know about the errors until I saw the earlier review here. However, there is no way to fix it. If the book is reprinted or a second edition is released, I can fix the errors, but not until then. I wish I could. I apologize to any who were confused by this problem.
There are 8 quotes replaced with underscores on 4 lines in Chapter 3, 2 quotes replaced with underscores on 1 line in Chapter 4, and 20 quotes replaced with underscores on 8 lines in Chapter 5. I have a list of the errors and corrections on my web site at janet.valade.com/php5errors.html.