One of the greatest aspects of the open source community is that people are eager to help you learn as much as you can, so that you can become an advocate as well. However, you probably should attempt to find answers to your questions before posing them to the community at large. This includes reading available manuals and FAQs, searching through mailing list archives, and visiting websites. Chances are good that someone else has had the same question you have.
The website for this book, and other books I have written, is http://www.thickbook.com/. You will find book errata, downloadable code from the books, recommendations for books and other items, and anything else I think up in my spare time. The book errata will help you to determine if your troubles are due to an error during printing, or if you should re-read the content of the section and try again.
PHP-related websites, newsgroups, and mailing lists are abundant, and the ones listed here are just a smattering of what's available.
The majority of these sites are maintained by normal people on their own time, so if you use any of their resources, try to give back to the community by helping others with their questions when you can, contributing code snippets to code repositories, and so forth.
The home of PHP is http://www.php.net. The annotated online manual is here, as well as the PHP FAQs, bug reports, links to ISPs that offer access to PHP, news articles, and much more!
Zend Technologies, the folks behind the Zend engine of PHP, have created a portal site for PHP developers. This personalized site not only showcases how you can build a high-traffic, dynamic site using PHP, but it also provides pointers, resources, and lessons on how to maximize the potential of PHP in all your online applications.
This site contains many user-submitted tutorials, news articles, interviews, and competitive analyses of server-side programming languages. Covers PHP as well as many other topics of interest to developers, such as servers and databases.
This is a very good tutorial site for intermediate and advanced PHP developers. It contains How To columns for real-world applications, such as "Building Dynamic Pages with Search Engines in Mind," "Generating Pronounceable Passwords," and tons more. Recommended!
A longtime favorite of PHP developers, this site contains development tricks and tips for many programming languages (just to be fair), as well as a content-management system for everyone to add their own code snippets, tutorials, and more! It has a great weekly newsletter and high traffic. Go contribute!
This is a bare-bones code repository, but who needs graphics when all you're looking for are code snippets? Borrowing from the "take a penny, leave a penny" mentality, you grab a code snippet to start with and then add your own when you feel confident in sharing.
The company that brings us Wired magazine also brings us HotWired, which spawned Webmonkey, a developer's resource site with a section devoted to PHP. Don't limit yourself to the PHP section of Webmonkey, because there's much information to be had in other sections as well.
Several high-traffic mailing lists are available for PHP discussion in English as well as other languages. Please remember your netiquette when asking a question: be polite, offer as many examples as you can (if you're describing a problem), provide your system information (if looking for a solution), and did I mention to say please and thank you?
You can find mailing list subscription information at http://www.php.net/mailing-lists.php. The English PHP mailing lists are archived and available for searching at http://marc.theaimsgroup.com/. Just look for the PHP-related lists under the WWW heading.
Sometimes, knowing other developers in real life can prove helpful. You can find a list of PHP user groups a http://www.phpusergroups.org/.