You know you've been waiting for it, here it is. The final installment of Chapter 7 of PHP in Action by Dagfinn Reiersol. Without further comment, here's the introduction to this section in Dagfinn's own words: "In this section we discuss an Iterator and a Composite."
Dagfinn briefly mentions what the two patterns are about - a "canned loop" and making tree structures easy. Check out the PDF for the remainder of the chapter.