I should point out that the topics presented here are research topics undertaken by IBM. Both presentations are the result of IBMers taking research and development experience in programming languages and applying that to PHP. And specifically, the challenges that PHP presents.
Brief overview ...
Julian's presented on static analysis of PHP, specifically, how static analysis can be used to identify security problems.
Graeme's presented on looking at the PHP runtime through the eyes of someone who has been developing Java VMs for the last decade.
Interesting stuff for folks interested in the nuts and bolts of dynamic languages and runtimes, and of course, specifically, PHP.
BTW, this was the same conference that Tim Bray presented on web frameworks, and then blogged about in Comparing Frameworks.