OOP in PHP

Basic OOP

Understanding basic object-orientation in PHP

abstract class A 
{
  function X()
}

interface B
{
  function Y()
}

class C extends A
{
  function Z() 
}

class D implement B
{
  - have to declare method Y
}

class E extends D
{
  - have to declare method Y
}

class F extends A implements B
{
  - has access to method X
  - have to declare method Y
}

class G extends C
{
  - has access to method X
  - has access to method Z
}

abstract class H extends A 
{
  - has access to method X (as well)
}

abstract final class Z
{

}

class Foo extends Z 
{
  - this cannot be possible because Z is marked as final
}

You can extend any class as long as its not marked as final.