As PHP has such a long history, it also means that there are many developers out there who are still standing with at least one foot in the past and are missing out on the bright and beautiful future of modern PHP. This book is for you, most of all.
The book is for existing PHP developers and CTO-level professionals who are working with PHP technologies, including legacy PHP, in production. The book assumes a reasonable level of knowledge of PHP programming and may require you to hit the PHP documentation to fill in gaps in your knowledge as they come up.