Context
I have a problem with my PHP website. To solve it, I want to step through the code. I am on a Windows machine using VSC as IDE. PHP runs in a docker container in parallel to an nginx container.

The Problem
I don’t know how to connect my VSC Debugger with the PHP runtime in the docker container.
I installed/enabled Xdebug and added a launch.json but the VSC Debugger does not react on page requests.

More details on what I tried
Xdebug seems to work. At least php -v (in the php container) returns

PHP 8.2.26 (cli) (built: Nov 21 2024 17:59:18) (NTS)
Copyright (c) The PHP Group
Zend Engine v4.2.26, Copyright (c) Zend Technologies
with Xdebug v3.4.0, Copyright (c) 2002-2024, by Derick Rethans

My xdebug.ini config is:

zend_extension=xdebug
xdebug.mode = debug
xdebug.start_with_request = yes
xdebug.client_host=host.docker.internal

My launch.json

{
  "version": "0.2.0",
  "configurations": [
    {
      "name": "Local docker Xdebug",
      "type": "php",
      "request": "launch",
      "hostname": "localhost",
      "port": 9003,
      "stopOnEntry": true,
      "pathMappings": {
        "/var/www/amc/plattform": "${workspaceFolder}\amc"
      }
    }
  ]
}

I then run ‘Local docker Xdebug’ and can see that the port is listening.
When I do a request, the page comes up, but the debugger does not connect/stop.

Any idea what is missing?

Update
Thanks to the great comments below I added a page with xdebug_info(); and enabled xdebug logging.

I get:

[Step Debug] Time-out connecting to debugging client, waited: 200 ms. Tried: host.docker.internal:9003 (through xdebug.client_host/xdebug.client_port).

So my container can’t connect to the host port. This is not the first time I want a container to connect to a host port. I am even doing this successfully in another container of the same docker compose file.

Inspired by this SO answer I added

 extra_hosts:
    - "host.docker.internal:host-gateway"

Still not lucky.

I don’t think that this is the way to go but I also tried to add 9003:9003 to the published ports of the container. I was surprised as the error was gone. Unfortunately VSC still did not react.

The info page showed

Debugger            Active  
Connected Client    host.docker.internal:9003

Looked positiv, but this is independant of the VSC Debugger. So if the Debugger is not listening, the info page still tells me “Debugger: Active” (I guess because my docker port publishing opens that port to pipe it into the container). Seems like xdebug only checks for the open port and not if a real debgger is listening on the other end.

The xdebug.log shows

[7] Log opened at 2024-12-02 22:04:21.868029
[7] [Config] WARN: Not setting up control socket with default value due to unavailable 'tsc' clock
[7] [Step Debug] INFO: Connecting to configured address/port: host.docker.internal:9003.
[7] [Step Debug] INFO: Connected to debugging client: host.docker.internal:9003 (through xdebug.client_host/xdebug.client_port).
[7] [Step Debug] -> <init xmlns="urn:debugger_protocol_v1" xmlns:xdebug="https://xdebug.org/dbgp/xdebug" fileuri="file:///var/www/amc/plattform/public_html/phpinfo-192837465.php" language="PHP" xdebug:language_version="8.2.26" protocol_version="1.0" appid="7"><engine version="3.4.0"><![CDATA[Xdebug]]></engine><author><![CDATA[Derick Rethans]]></author><url><![CDATA[https://xdebug.org]]></url><copyright><![CDATA[Copyright (c) 2002-2024 by Derick Rethans]]></copyright></init>
[7] [Step Debug] -> <response xmlns="urn:debugger_protocol_v1" xmlns:xdebug="https://xdebug.org/dbgp/xdebug" status="stopping" reason="ok"></response>
[7] Log closed at 2024-12-02 22:04:21.893973

Any ideas left what I can try?