ReflectionParameter::isDefualtValueAvailable() always returns false if parameters are out of order

[Crell]

Description

The following code:

<?php

declare(strict_types=1);

class Dummy
{
    public function __construct(public bool $routable = true, public int $junk)
    {
    }
}

$rConstructor = new \ReflectionClass(Dummy::class)->getConstructor();

$rParams = $rConstructor->getParameters();

var_dump($rParams[0]->isDefaultValueAvailable());

Resulted in this output:

bool(false)

But I expected this output instead:

bool(true)

More precisely, it seems that when a required parameter comes after an optional parameter, something in reflection goofs and it isn't able to see the default value for the optional parameter.

I suspect this hasn't been run into before, because it's so rare to have a constructor that has its parameters backwards. It doesn't actually error for me, as I'd expect it to, but the reflection gets goofy as shown above. (In my case I'm only creating the object via reflection, so didn't even realize I had the parameters in a bad order.)

PHP Version

8.4.2

Operating System

Ubuntu 22.04

[nielsdos]

Because the required param comes after the optional one, the optional one becomes required.

[damianwadley]

...which PHP would have mentioned, given appropriate error reporting settings:

Deprecated: Optional parameter $routable declared before required parameter $junk is implicitly treated as a required parameter