Sebastian Bergmann has posted a current state of AOP for PHP summary on his blog today, a look at a few resources and an addition of one of his own.

I know about four existing approaches to faciliate Aspect-Oriented Programming with the PHP Programming Language:

• PHPAspect
• Aspect-oriented PHP
• aspectPHP
• AOP Library for PHP

But, as was previously mentioned, he's not happy with the current implementations, so he's working up his own - AspectPHP...