Answer 1: The decision between the two solutions depends on your specific use case and your team's preferences. The magic methods approach, A, may be more flexible as it allows for more complex logic to be executed when the dynamic properties are set or accessed. However, the attribute approach, B, is simpler and less prone to errors, and it would work just as well for most use cases.
Answer 2: One way to identify all the classes that undergo this abuse would be to search the codebase for instances of dynamic property assignments, such as $foo->some_new_property = 42;. This can be done using a text editor with a "find in files" feature or using a command line tool such as grep. Additionally, some IDEs, such as PhpStorm, have built-in features to search for specific patterns in the codebase, which could be used to identify the dynamic property assignments.
Another approach is to use a code analysis tool that can identify instances of deprecated or problematic code. Some popular examples include Psalm, PHPStan, and Phan. These tools can often be integrated with your development environment, such as with a plugin for your text editor or IDE, and can help you identify potential issues with the codebase, including instances of dynamic property assignments.
Overall, it's important to keep in mind that upgrading to PHP 8.2 may involve changes to your codebase, so it's essential to thoroughly test your application before deploying it to a production environment.