Personally I'd prefer protected friendship only. Or at least by default. Perhaps make an option to declare a private friend explicitly. I think it would be beneficial to have an explicit distinction between accessible and truly private members. And since inheritance is not a great practice in most cases (i.e. composition over it), having a protected method/property in some systems that extensively use composition could indicate that they are used in some friendship relation. While private stay private.

Personally I'd prefer protected friendship only. Or at least by default. Perhaps make an option to declare a private friend explicitly. I think it would be beneficial to have an explicit distinction between accessible and truly private members. And since inheritance is not a great practice in most cases (i.e. composition over it), having a protected method/property in some systems that extensively use composition could indicate that they are used in some friendship relation. While private stay private.

Not going to do that, the idea is that friends can access private parts
"inheritance is not a great practice in most cases" may be your view, but there is plenty of inheritance in the PHP ecosystem
And nothing is truly private when reflection is always available