In PHP OOP is it a must to use all of the methods in an abstract class or just some?

[spence911]

I can't find an explicit answer on this anywhere, but when you create a child class from an abstract class must you use ALL of the methods that are inside the abstract class in the new child class? Or are these methods just available to the child class to pick and choose?

[Jacques1]

If the child class itself is not abstract, it must implement all abstract methods and may overwrite any of the other methods.