PHP 8.5 Support

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PHP 8.5 will be released November 20, 2025. Compared to previous releases, the list of changes that will affect us seem to be minimal:

According to https://php.watch/versions/8.5:

Deprecated functionality:

• All MHASH_* constants deprecated
• Non-canonical scalar type casts (boolean|double|integer|binary) deprecated
• Returning non-string values from a user output handler is deprecated
• Emitting output from custom output buffer handlers is deprecated

Of those, it seems that only the second one may be relevant to Backdrop. Doing a quick search I found that casting as (boolean) is rare but happens in a few places. Other scalars seem to be fine.

We should increment our supported PHP version to 8.5, and bump the test runner to run on 8.5 when ready.

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Note that DDEV v1.24.10 now includes built-in support for PHP 8.5, which should make testing this locally a lot simpler.

It also looks like the https://github.com/shivammathur/setup-php project that we use to run PHP in GitHub Actions also has support for PHP 8.5. So it does not seem that we would have any blockers.

[indigoxela]

I have 8.5 available in my dev environment and volunteer to take over here.

Trivial changes? Not entirely... 😁
There's some small hiccups in our db abstraction layer (easy to fix), and the casting in few places, of course, but I also saw some glitches in Views, which require a little more research. Might be easy, but eventually not.
And I guess, there will be more findings, when running all the tests. We'll see.

PHP 8.5.0 RC 5 has been released yesterday, and that will probably be the last RC before stable.

[quicksketch]

Thank you @indigoxela! Everything is looking good so far!

I apologize if I underestimated the work. I did not see that PDO set of changes coming.

[indigoxela]

I apologize if I underestimated the work.

No problem. 😀 It has to happen regardless. There's sufficient time and it's feasible, just slightly more effort - coding and review.
I like, how PHP gets more picky (more diligent) with every minor version - but it causes work, of course. 🤷

[indigoxela]

Step by step...

One of the trickier problems has to do with Layout::getPath(). It claims to always return string, but that's not true - for the default admin layout, for example, the path is NULL. I guess, there are more null-paths. This leads to some odd array keys, and I'm not sure, how to properly deal with that. @quicksketch

Edit: casting where needed seems appropriate to me. But update doc block that it can be null.

Another one, but maybe not urgent: I don't think that Query::__wakeup() ever worked as expected. We might change that magic method, or stick with our workaround, but that's all a little above my head. 😉