PHP is the most popular language for web development, but a common criticism against it used to be that it lacked a suitable debugger. Developers using languages like Java and C# enjoy a powerful suite of debugging tools, often integrated directly with their IDEs. But the disconnected nature of web servers and PHP IDEs prevented us from having many of the same tools available. We manually added debug statements in our code… until Xdebug filled the void. Xdebug is a free and open source project by Derick Rethans and is probably one of the most useful PHP extensions. It provides more than just basic debugging support, but also stack traces, profiling, code coverage, and so on. In this article you’ll see how to install and configure Xdebug, how to debug your PHP application from Netbeans, and how to read a profiling report in KCachegrind.