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DevShed starts up a new series of tutorials today with this article, a look at how to build a query processor class for networking with PHP.
The networking query application that I plan to build will be encapsulated within a single PHP 5 class, but you can easily modify its complete source code in order to work with PHP 4. As I said before, this application should be considered a practical introduction to using many PHP built-in functions included in the corresponding PHP network library, so if you want to learn how to use these functions, this series might help you to start quickly including them in your own applications.
The app gives examples of converting hostnames to IP addresses (and back), defining two of the service methods in the class, and plugging them into a working example. It basically still only does the hostname/IP converstions, but it also lists out the services and which ports their on.