On PHPMaster.com there's a new tutorial about array operators in PHP, more so how the usual operators interact with arrays.

Operators in PHP can be organized into seven different categories: arithmetic, assignment, bitwise, comparison, error control, execution, incrementing/decrementing, logical, string, array, and type operators. This article details working with array operators, but also covers how some of the other operators work when used with arrays.

• array union (plus)
• equality (double equals)
• identity (triple equals)

They also talk briefly about some of the other PHP operators with arrays (like subtraction, multiplication and division) and some of the conversions that PHP does when they're used.