Notes when using PHP abstract classes to inherit abstract classes

When the PHP abstract class inherits the abstract class, note that when the abstract class inherits another abstract class, the abstract method of the abstract parent class cannot be rewritten in the abstract class. This can be understood as an extension of an abstract class.

The following example demonstrates that when an abstract class inherits from another abstract class, you do not need to override the abstract method.

After an abstract class is inherited, its abstract methods cannot be overwritten. If a rewrite occurs, the system reports an error.

Program running result:

Fatal error: Can't inherit abstract function User::setSal() (previously declared abstract in VipUser) in E:\PH

Conclusion: the abstract class inherits the abstract class to extend the abstract class.

The code above extends the methods of the parent class.