vscode-php-xdebug configuration #7574 deprecates the simple serverSourceRoot localSourceRoute keys, and moves to have a hash like

"pathMappings": {
   "/var/www/html": "/path/to/html",
   "/app": "/path/to/app"
}

References: https://github.com/xdebug/vscode-php-debug?tab=readme-ov-file#supported-launchjson-settings and https://github.com/xdebug/vscode-php-debug/blob/bcb2ba1b806be0bbfe04b766f2cf31303dd5dc00/package.json#L256

@mattriverm noted:

To support a table of pathmappings like the below example, the helix config (DebugArgumentValue) needs to be extended.

[[language.debugger.templates]]
name = "Listen for Xdebug"
request = "launch"
completion = ["ignored"]

[language.debugger.templates.args]
port = "9001"

[language.debugger.templates.args.pathMappings]
"/some/path/on/server" = "/some/path"
"/another/server/path" = "/another/local/path"

I believe it is a simple change, if there is an issue filed I could attempt a PR.
Regarding substitution, not sure. Might be simple to look for {workspaceFolder} and replace with cwd, or helix concept of root folder.

Originally posted by @mattriverm in #7574 (reply in thread)