I am currently in Sofia attending the webtech conference. However some of the talks are in Bulgarian which makes it quite hard to follow. (There is translation available, but it is still not easy). So, instead of going to the sessions I finalized some optimization patches for Xdebug . I managed to find and fix some performance bottlenecks with cachegrind. Xdebug usually tries to figure out which variables are available in a specific function's scope by iterating over the op array that is being excuted. However, in many cases this is totally useles as the information is never used in any way. With the patch Xdebug will only try to figure out this information when either remote debugging is enabled, or when the setting xdebug.show_local_vars is activated. This speeds up certain applications by as much as 50%. This patch, and many others, made it into Xdebug 2.0.0beta6 which I just released through PECL. The source code is also avaible through the Xdebug website.