php abstract class extending another abstract class

Question

Is it possible in PHP, that an abstract class inherits from an abstract class?

For example,

abstract class Generic {     abstract public function a();     abstract public function b(); }  abstract class MoreConcrete extends Generic {     public function a() { do_stuff(); }     abstract public function b(); // I want this not to be implemented here... }  class VeryConcrete extends MoreConcrete {     public function b() { do_stuff(); }  } 

( abstract class extends abstract class in php? does not give an answer)

Answer 1

Yes, this is possible.

If a subclass does not implements all abstract methods of the abstract superclass, it must be abstract too.

Answer 2

It will work, even if you leave the abstract function b(); in class MoreConcrete.

But in this specific example I would transform class "Generic" into an Interface, as it has no more implementation beside the method definitions.

interface Generic {     public function a();      public function b(); }  abstract class MoreConcrete implements Generic {     public function a() { do_stuff(); }     // can be left out, as the class is defined abstract     // abstract public function b(); }  class VeryConcrete extends MoreConcrete {     // this class has to implement the method b() as it is not abstract.     public function b() { do_stuff(); } }