KCachegrind is an excellent tool for reading (or, rather, browsing, as this process is highly interactive) profiling reports generated from a multitude of applications, including the web3tracer PHP profiler.

KCachegrind usually comes bundled into the KDE desktop bundles (package kdesk on RHEL). We have also compiled Windows KCachegrind for the Windows users' convenience. Having been developed on top of QT, the tool can probably be ported to most other platforms, so you can take your PHP profiler's output for analysis from the server to your desktop of choice. KCachegrind is an interactive tool that allows you to explore the traces gradually and in detail. This also means it needs a graphical GUI to work.

Its main fetures are:

• Visual rendering of the call tree, with partial representation to filter relevant data
• Complex statistics regarding program execution
• Ease of use
• Possibility to export call trees as images

The PHP profiles generated with the callgrindWriter can be browsed and visualized using KCachegrind, in a straight-forward manner. All you need to do is open the files generated by the extension in KCachegrind.

The output generated by web3tracer is particular in that it comes already processed for recursion. Tha callgrind file format does not provide enough data to properly detect and handle recursive functions, and so web3tracer PHP profiler pre-formats the output wit recursive call nodes and call decoupling, for easiest visualisation.

In the next subsections we show practical examples of using the PHP profiler to generate and interprete meaningful execution data, be sure notto skip them.