ext/standard: validate mode in array_filter()

[jorgsowa]

Validates mode in the function array_filter() and creates complementary ARRAY_FILTER_USE_VALUE without exposing it as a PHP constant.

[bukka]

I think this might be safer to go through deprecation first.

[bukka]

Technically it's a BC break as the invalid mode is currently ignored.

[jorgsowa]

Makes sense. I will wait for PHP 8.5. I was following a similar change with round() which didn't need RFC: #12252

[cmb69]

A deprecation is certainly more user friendly, but requiring the RFC process for this appears to be overkill. After all, users are not supposed to pass nonsense to well documented functions.

[bukka]

Well just that something users are not supposed to do, does not mean that it's not a BC break. In my opinion it is a BC break and as such we should go through the deprecation. I agree that doing RFC is overkill but I don't think we need RFC if we get some sort of agreement.

[iluuu1994]

LGTM. I wouldn't object to this in a minor version, but @bukka should confirm whether he does. If so, you can just change the error to a deprecation. According to the policy:

https://github.com/php/policies/blob/main/release-process.rst#feature-selection-and-development

However, any change that breaks user-facing backward compatibility MUST go through the RFC process.

From a pedantic PoV, this is breaking. In that case, this would even need an entry in the deprecation RFC.