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Setting up Xdebug with Lagoon#

Enable Xdebug extension in the containers#

The Lagoon base images are pre-configured with Xdebug but, for performance reasons, the extension is not loaded by default. To enable the extension, the XDEBUG_ENABLE environment variable must be set to true:

Activate Xdebug Extension#

The default Xdebug configuration requires a "trigger" to activate the extension and start a session. You can view the complete documentation for activating the debugger but the most straightforward instructions are below.


The php-cli image is configured to always activate Xdebug when it’s enabled, so there is nothing else that needs to be done. Running any PHP script will start a debugging session.


Install a browser extension to set/unset an activation cookie.

Make sure the activation cookie is set for the website you want to start debugging.

Configure PHPStorm#

  1. PHPStorm is configured correctly by default.
  2. Click the “Start Listening for PHP Debug Connections” icon in the toolbar.
  3. Load a webpage or run a Drush command.
  4. On first run, PHPStorm should pop up a window asking you to:
    1. Confirm path mappings.
    2. Select the correct file locally that was triggered on the server.

Configure Visual Studio Code#

  1. Install the PHP Debug extension by Felix Becker.
  2. Follow the instructions to create a basic launch.json for PHP.
  3. Add correct path mappings. For a typical Drupal site, an example would be:

    "pathMappings": {
      "/app": "${workspaceFolder}",
  4. In the Run tab of Visual Studio Code, click the green arrow next to “Listen for Xdebug

  5. Load a webpage or run a Drush command.


  • Verify that Xdebug extension is loaded. The best way to do this on a Drupal site is to check the PHP status page. You should find a section about Xdebug and all its settings.

phpinfo results

  • Verify the following settings:
Directive Local Value
xdebug.mode debug
xdebug.client_host host.docker.internal or your IP address
xdebug.client_port 9003
  • Enable Xdebug logging within the running containers. All you need is an environment variable named XDEBUG_LOG set to anything to enable logging. Logs will be saved to /tmp/xdebug.log. If you are using the lagoon-examples then you can uncomment some existing lines.
  • Verify you have the activation cookie set. You can use the browser tools in Chrome or Firefox to check that a XDEBUG_SESSION cookie is set.
  • Verify that Xdebug is activated and attempting to start a debug session with your computer. You can use the nc -l 9003 command line tool to open the Xdebug port. If everything is configured in PHP correctly, you should get a Xdebug init response when you load a webpage or run a Drush command.
  • Verify that the xdebug.client_host has been set correctly. For local debugging with Docker for Mac, this value should be host.docker.internal. For remote debugging this value should be your IP address. If this value was not correctly determined, you can override it by setting the DOCKERHOST environment variable.
  • When using Lando locally, in order to debug scripts run from the CLI you must first SSH into the CLI container via lando ssh. You won’t be able to debug things by running lando drush or lando php.

Mac specific troubleshooting#

  • Verify that Docker for Mac networking is not broken. On your host machine, run nc -l 9003, then in a new terminal window, run:

    Verify Docker for Mac networking
    docker-compose run cli nc -zv host.docker.internal 9003

    You should see a message like: host.docker.internal ( open.

Linux specific troubleshooting#

  • Ensure the host host.docker.internal can be reached. If docker has been installed manually (and not through Docker Desktop), this host will not resolve. You can force this to resolve with an additional snippet in your docker-compose.yml file (instructions taken from this blog post):

    docker-compose.yml alterations for Linux
            host.docker.internal: host-gateway
            host.docker.internal: host-gateway

Xdebug 2#

If you're running older images you may still be using Xdebug version 2. All the information on this page still applies, but some of the configuration names and values have changes:

v3 v2
xdebug.mode xdebug.remote_enabled On
xdebug.client_host xdebug.remote_host host.docker.internal or your IP address
xdebug.client_port xdebug.remote_port 9000