Xdebug is a debugging tool for PHP. It provides step-debugging and a whole range of development helpers, such as stack traces, a code profiler, features to dump the full execution of your script to a file, and more.
Xdebug requires a supported version of PHP. For installation it requires the pecl tool (available through the php-pear package), unless your Linux distribution has an Xdebug package (php-xdebug).
On most Linux distributions you can install Xdebug through its package manager. You can also compile from source with the pecl tool through pecl install xdebug. The latter also works for MacOS as long as PHP is installed with Homebrew.
On Windows, you need to download a binary. Use the Wizard.
Unless you have installed Xdebug with a package manager on Linux, you also need to add the following line to your php.ini file, or create a new Xdebug specific ini file xdebug.ini in the conf.d directory. In either case, it needs the following line added:
zend_extension=xdebug
For more extensive installation instructions, see the documentation at https://xdebug.org/docs/install
Most features in Xdebug have to be opted in into. Each feature has a specific opt-in. For example to use the step debugger you need to set xdebug.remote_enable=1 in your configuration file. The step debugger requires an IDE (client), of which there are many available.
The documentation has instructions for each of Xdebug's features: https://xdebug.org/docs/ and a full list of settings is also available there.
Xdebug is written in C, and extensive knowledge of PHP's internals is necessary to be able to contribute. Contributing guidance is available separately.
Before you begin to contribute, please reach out first. Either through email (address at the bottom), an issue in the issue tracker or preferably through IRC on Freenode's #xdebug channel.
If you are familiar with compiling PHP extension from source, have a local checkout of Xdebug's GitHub repository, and have compiled Xdebug in that directory following the instructions under installation you can run Xdebug's tests by running:
php run-xdebug-tests.php
The test framework requires that the PHP binary on the path has Xdebug loaded, with remote debugging enabled through xdebug.mode=debug. It is possible to skip remote debugging tests by exporting the SKIP_DBGP_TESTS=1 environment variable.
The SKIP_UNPARALLEL_TESTS=1 can be used to skip tests that can not run in parallel environments, and the SKIP_SLOW_TESTS=1 environment variable to skip slow tests. The OPCACHE environment variable can either be yes or no and controls whether the test framework enables or disables OpCache.
Xdebug is released under The Xdebug License, which is based on The PHP License. It is an Open Source license (though not explicitly endorsed by the Open Source Initiative).
Xdebug has extensive documentation on its website. There are over a hundred settings and many functions documented. Please have a look through the wealth of information that Xdebug can provide to make your every day development with PHP easier.
For questions regarding Xdebug, please use StackOverflow, and tag your question with xdebug.
You can also find ad-hoc and sporadic support on IRC: freenode/#xdebug.
You can do that with your favourite client, or by using their webchat.
If you think that you encountered a bug, please file a detailed bug report at https://bugs.xdebug.org. You are required to create an account, this is so that you can be contacted for additional information and to keep out spam.
Derick Rethans — derick@xdebug.org