PhpStorm‑Docker Debugger: Does Xdebug remote_connect_back Follow Container Network Mode?

Answer

PhpStorm always injects XDEBUG_CONFIG with remote_connect_back=0 when launching a Docker debug configuration. This value does **not** change when the container’s network mode is switched between bridge and host; it remains 0 regardless of the mode.

Likely explanation

PhpStorm’s Docker integration injects the XDEBUG_CONFIG environment variable to enforce a secure debugging setup, forcing Xdebug to connect back only to the IDE host (via host.docker.internal or an overridden remote_host). This injection is performed unconditionally, so the plugin does not inspect or adapt to the container’s network mode.

Confirmed facts

• The injected variable sets remote_connect_back=0 and remote_host=host.docker.internal (or a user‑provided value).
• Changing the Docker run configuration’s Network mode from bridge to host (or vice‑versa) does **not** alter the injected XDEBUG_CONFIG; the value stays as originally set.
• There is no UI option in PhpStorm’s Deployment/Debugger settings to control remote_connect_back; users must adjust it manually via environment variables, Docker run options, or by editing php.ini inside the container.
• When using host network mode, the default remote_host (host.docker.internal) may not resolve, requiring an explicit override (e.g., remote_host=localhost or the host’s IP).

Steps to verify

1. Start a Docker debug session from PhpStorm.
2. Exec into the running container and run echo $XDEBUG_CONFIG (or check phpinfo()) to see the current value.
3. Confirm that remote_connect_back=0 appears.
4. Stop the session, change the container’s Network mode in the Docker run configuration (bridge ↔ host), and restart the debug session.
5. Repeat the echo $XDEBUG_CONFIG check; the value will remain unchanged.
6. If you are using host network mode and the debugger fails to connect, override XDEBUG_CONFIG (e.g., set remote_host=localhost) in the Docker run configuration’s Environment variables field and verify the connection works.

If you encounter connection failures specifically when using host network mode, please let me know so I can advise on the appropriate remote_host override.