On Slashdot, Sebastian Bergmann has a book review of one of the latest PHP-related offerings from SAMS Publishing - Sare Golemon's "Extending and Embedding PHP".
"Extending and Embedding PHP" by Sara Golemon, a long-time contributor to the PHP project, remedies the fact that the internals of PHP are far from being as well documented as the rest of PHP. It brings writing extensions for PHP "to the masses", so to speak.
Sebastian covers the contents of the book, one chapter at a time - everything from "Memory Management" out to the "Streams" chapters. His opinion of the book is a good one, too, noting that it brings a topic that could have been rendered unreadable by the wrong author into the realm of "the masses" with plenty of explaination and code throughout.