Yes, extending a class means your child classes inherit all properties and methods. No, if they are declared private, then only the parent class has access to them. This is why I recommend to give them the protected visibility so derived classes can still have access to those properties. Note that even private properties are inherited, they're just not accessible.

Actually, abstract classes are a very powerful way to implement what's known as polymorphism, or the ability to use different objects in the same way. This Wikipedia article on Object Oriented programming states that and more.

Think of abstract classes like this: you want to create an object that handles data storage. Period. The interface should be the same regardless of how the class stores data. So you can have an abstract class named 'DataHandler' with methods like 'putData' and 'getData', etc. You can derive this abstract class into a class that interacts with databases, or a class that stores and retrieves data from a flat file. These classes can be further derived into classes that specify what type of database, if the file is XML, JSON or regular text, etc. But the calling object will still use the same 'getData' and 'putData' methods, so it's totally flexible if you should want to switch how you store data.

Static method calls are essential in most OO programming; I use them everyday.

The bottom line; unless you plan on going all OO in your PHP code, or switch to Java or C#, all of this may not be relevant to you.

__________________

I reject your reality, and substitute my own.