Make it compatible with PHP 8.2

[elias-playfinder]

This prevent the deprecated error:

Creation of dynamic property OpenActive\\Validators\\RpdeEnumValidator::$classname is deprecated

[nickevansuk]

Should 8.2 also be added to CI along with this?

https://github.com/elias-playfinder/models-php/blob/4689f4462b9993c5d4e3d42272bf1025891db341/.github/workflows/tests.yaml#L14

[drinkynet]

@nickevansuk Here is some information on the PHP 8 Dynamic properties deprecation: https://php.watch/versions/8.2/dynamic-properties-deprecated

There are 3 options:

• The best one is to declare the property as in this PR.
• The worst one is probably to hide the deprecation notice with the #[AllowDynamicProperties] attribute, but it'll stop it failing until a version of PHP where it's not allowed.
• If you genuinely need to set dynamic properties then the __set() and __get() magic method strategy is the way to go. You see this sort of pattern in ORMs because a data model may not know its structure till it has the data. e.g.: https://github.com/illuminate/database/blob/81a6d9b4ed991afdf3ce476b0049ad4fddf7d8ed/Eloquent/Model.php#L2242

[nathansalter]

Fine with this to be merged but we do need to fix the CI builds first

[drinkynet]

If you want the 5.6 test to pass you'll need to change it to:

protected $classname;

type declarations for properties are 7.4+

[elias-playfinder]

👍 Sure. I've changed and added the type as notation instead