On DevShed today, there's an introduction to PHP posted - an excerpt from the O'Reilly book "Web Database Applications with PHP and MySQL", written by Hugh E. Williams and David Lane.

This chapter is the first of three that focus on the PHP scripting language. This chapter describes the PHP language basics. Chapter 3 describes PHP’s support for arrays, strings, and other data types, and Chapter 4 introduces object-oriented programming in PHP.

They really start with the basics here, "hello world" and all. They also cover the creation of scripts, expressions/operators/variables, swtich(), looping, type conversion, user-defined functions, static variables, and using/managing included files.