This extension adds operator overloading support to PHP 5. I don't think operator overloading fits the "PHP spirit" and as such I speculate it probably won't ever make it into the core. Regardless, it's interesting that this extension is now available and certainly makes for some fun experiments, especially if you're already familiar with techniques from languages like C++.
He gives some sample code, and mentions the "magic methods" the extension allows. Later in the post, he also looks at a related package (also by Sara) that allows for self-modifying code in PHP - pecl/runkit.