Xdebug is a PHP extension automatically enabled in the Vagrant VM that allows for step-by-step code debugging, code profiling, and code tracing. For more information about the features of Xdebug, see xdebug.org.

For the default configuration, it is recommended to use an extension to enable one of the Xdebug modes; see https://www.jetbrains.com/help/phpstorm/browser-debugging-extensions.html for a list of extensions that can be used with Xdebug. When using one of the Xdebug Helper extensions, the specified mode should be selected while on a page (Debug/Profile/Trace) from your local Submitty installation to use it.



See PhpStorm Setup Instructions#Enable PHP Debugging using xdebug for details on how to enable and use Xdebug in PhpStorm.


In order to use debug mode with Xdebug, the Remote SSH extension or equivalent extension may need to be used to connect directly into the Vagrant machine. Additionally, the PHP Debug extension should be installed.

Create a file titled launch.json under the .vscode folder in the root of the currently opened folder, creating the .vscode folder if it does not exist, and paste the following into the file:

    "version": "0.2.0",
    "configurations": [
            "name": "Listen for Xdebug",
            "type": "php",
            "request": "launch",
            "port": 9000,
            "pathMappings": {
                "/usr/local/submitty": "/usr/local/submitty/GIT_CHECKOUT/Submitty"

After this, Xdebug can be started by going to the Run and Debug tab (play button with a bug on the sidebar), selecting Listen for Xdebug in the dropdown menu and clicking the play button. A short bar will appear that lets you control and end the debug session. To create breakpoints, click to the left of the line numbers; inline breakpoints can be created by right clicking and selecting Add Inline Breakpoint.


After visiting a webpage with the profiling flag enabled, profiler results will be stored by default under /.vagrant/Ubuntu/profiler, under files that are titled cachegrind.out.<number>. These files can be analyzed using PhpStorm’s built in tools or using a tool such as KCacheGrind/QCacheGrind.

Note: It is recommended to only enable profiling when needed as profiling increases load times and the files generated take up a significant amount of space.


Follow the steps under Debug to enable debugging with PhpStorm, and then follow https://www.jetbrains.com/help/phpstorm/profiling-with-xdebug.html#snapshotLocation, starting at Specify the location for storing accumulated profiling data.


To view the profiled files in a visual format, programs such as KCacheGrind/QCacheGrind can be used - a Windows binary is available here: https://sourceforge.net/projects/qcachegrindwin/, and macOS/Linux users can use Homebrew to install it with brew install qcachegrind.