Summary

In this hour, you saw how to use environment variables to learn more about your visitors. If you don't have access to a user's hostname, you should now be able to use gethostbyaddr() to acquire it.

You learned some of the basics about the negotiation that takes place between a client and server when an HTTP connection is made.

You learned how to use fopen() to get a document from the Web and how to use fsockopen() to make your own HTTP connection. You should also be able to use fsockopen() to make connections to other network services. You learned how to use mail() to send email from your scripts. Finally, you peeked below the hood to examine streams, the mechanism by which data functions deal transparently with multiple protocols.

So far in this book, we have concentrated on text. In the next hour, we look at some functions that enable us to use PHP to contruct and manipulate images.