The PHP Core and its library of extensions contains other, less commonly used or less frequently available API calls than those listed here. If you need a bit of functionality that's already being performed by a core function or some extension, refer to its header files and see if it's not also exported to internals-space for use by extensions or embed wrappers like your project.
Appendix D, "Additional Resources," will highlight just these types of "How'd they do that?" approaches to learning by example. First though, you'll take a look at a set of boiler plate templates for doing the most common tasks that you can freely modify and use in your own projects.
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