Description:
------------
https://github.com/php/php-langspec/blob/master/spec/14-classes.md#classes

Derived classes get mentioned a fair amount throughout section 14 but there is no one place that really pins down a lot of the rules about how derived classes work. Here are some questions I don't think the spec really answers that it should answer: 

 - What happens when a base class and a derived class both define a public instance property named $x? Specifically how does storage work in such cases? 
 (It appears that only one $x is allocated, and it has the initial value of the most-derived declaration.)

 - What happens when a base class defines a private instance property named $x and then a derived class declares a public or protected or private instance property named $x? Specifically how does storage work in such cases? (It appears that two $x’s are allocated.)

 - What happens when a base class defined a static property named $x and then a derived class declares a static property named $x? How does storage work in such cases? 

 - If the method body for C::foo defines a function static variable, and then D derives from C and D does not override method foo, how does storage for the function static work? 

 - What if there is a private instance method named "bar" and a non-private instance method named "bar" within the same inheritance hierarchy, and then a call site somewhere in the class hierarchy calls instance method "bar". Which "bar" gets called?