We've all experienced performance issues and we would typically turn to a profiler. Whether that's something in userland, or a tool like xdebug or xhprof, the reason is the same: to figure out why our code is slow. This talk will take that inspection a step further and look under the hood of PHP, at the C internals, for common performance problems. If you've ever wanted to know exactly what your code is doing, and why ++$i is faster than $i++, this talk is for you. Note: This is an advanced talk, you should be extremely familiar with PHP and have some experience with profiling if you are to get the most from this talk.