One of the disadvantages of developing against an open source project like PHP is the lack of paid support channels. There's no guarantee of response time on queries, and no assurance that the person who's answering you actually knows what he is talking about.
One of the great advantages of developing against an open source project like PHP is also the lack of paid support channels. Because PHP is in widespread use by so many individuals who are actually familiar with its internals, finding a reliable source of information on a given topic usually requires nothing more than asking.
Bear in mind that most of these resources are volunteers helping out for nothing more than the satisfaction of passing on knowledge. Ask nicely and be patient in waiting for answers; you'll catch more bees with honey than you will with vinegar.
PHP Mailing Lists
The most official of these information resources are the mailing lists hosted by the PHP project itself. Mailing lists such as email@example.com and firstname.lastname@example.org are routinely monitored by the PHP language developers themselves and answers to any well asked question can usually be had within a day, if not within the hour.
The pecl-dev list is typically the best place to go for instruction on how to accomplish a specific task in an extension or embedding project. Don't let the name of the list put you off; it's all right to ask for help in developing closed-source and proprietary code. PECL is simply the driving force behind most projects developed here.
The internals list, on the other hand, aims to focus on developments in the language itself. At the time of publication of this book, this list is focused on the overhauls taking place for PHP6. If you want to keep an eye on what APIs are being changed and how your extension or embed project will need to adapt to fluctuations in the language, this is the list to watch.
Several networks carry general purpose PHP scripting support channels. In some of these, such as the ##php channel on Freenode, you'll find a few individuals with experience developing with the PHP internals. Spend some time browsing through the IRC networks out there and you'll probably find someone up at any given time of day or night to answer that 11th hour question.
The PHP Life Cycle
Variables from the Inside Out
Setting Up a Build Environment
Your First Extension
Working with Arrays and HashTables
The Resource Data Type
Startup, Shutdown, and a Few Points in Between
Diverting the Stream
Configuration and Linking
Setting Up a Host Environment
Appendix A. A Zend API Reference
Appendix B. PHPAPI
Appendix C. Extending and Embedding Cookbook
Appendix D. Additional Resources