The third part of a three-part introductory course to PHP have been put on on IBM's developerWorks site.

Part one looks at the basics of building a PHP script; syntax, HTML forms, and database connections.

Part two takes you from the most basic PHP script to working with databases and streaming from the file system by documenting the building of a document workflow system

And in this new tutorial you will learn about using HTTP authentication, streaming files, and how to create objects and exceptions.