Naming issue: attribute

[samdark]

We call data properties "attributes" because in both Yii1 and Yii2 these were called so. The issue is that PHP now has https://www.php.net/manual/en/language.attributes.overview.php so the name became very confusing.

Renaming would require breaking BC so that's for the next major version.

Thanks, @vudaltsov for pointing it.

[arogachev]

I used "attributes" / "PHP attributes", but agree that the naming can be improved.

[vjik]

Done by #730