If APP_RUNTIME is not defined the runtime class will be the one defined in composer.json’s extra.runtime.class, or the SymfonyRuntime by default.

If the goal of this PR is only to display APP_RUNTIME’s value, the profiler already has a Server Parameters tab in the Request panel.

Hey thx for trying that
Indeed this env var alone is not worth it
My main idea in the issue was if we can display, in the profiler or perhaps also the console about command, the real runtime behind the scene from wherever it can come from
(Dont know the feasability thought)

The PR now displays the resolved runtime class — it checks APP_RUNTIME, then composer.json's extra.runtime.class, and finally falls back to Symfony\Runtime\SymfonyRuntime if none are set. So it shows the actual runtime behind the scenes, not just the env var.

About the implementation, this relies too much on implementation details.
A better implementation my be to rely on the global $runtime variable.

BUT, I'm not sure what this info could be useful for. Any details about that?

The runner might be a more useful thing to show, because then one can see if they're running frankenphp or etc.
And this can be known by checking the first frames of any stack trace.

@nicolas-grekas ftr, when I created the issue I was testing locally frankenphp with worker mode, and wanted to check if the runtime was the proper one, and didnt saw any thing related in profiler, thus opening this issue

OK, so showing the runtime won't help. The SymfonyRuntime is able to handle both PHP-FPM and frankenphp.

Closing for history. PR welcome I suppose to show the runner instead.
Thanks for submitting!