Guilherme Blanco has submitted a note about a project he's been working on, especially pertinent due to some of the discussion flying around on the subject - his Transparent PHP AOP project.
My AOP package implements this magic with PHP code in a transparent way. This means that the original code does not need to be altered in a special way to add or remove the aspects. It is only necessary to add a comment line to define the location of the pointcuts.
This package is actually a smart caching compiler. It preprocesses the original code to locate the pointcuts. Then it generates a new version that may include the code that implements the aspects that I want to enable.
In his blog entry, there are links to the package downloads and the official manual to help get you started as well as more details on some of the functionality behind the magic.