I teach an introductory web sequence that includes some PHP. I use this book because it has good explanations instead of doing lite coverage of everything that's done on the web.
The book's website is hosed, however. Ignore it as they have ignored my pleas for fixing it. By Fall I'll probably have a version that does what the book says it does.
Thin is OK if the book is good. This book is both.
As you work through the book, get acquainted with the manual at [...] - it'll take you the next step.