How to use the abstract keyword in php

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Detailed explanation of php abstract keywords

1. The way of abstract modification is abstract method, and the decorated class is abstract class.

two。 Only the declaration of the method. No implementation of the method is abstract.

3. As long as one method in a class is an abstract method, the class must be abstract.

4. The special thing about abstract classes is that they cannot be instantiated.

5. If a subclass inherits an abstract class, all abstract methods of the parent class must be reimplemented, otherwise instantiation is not allowed

6. There are no abstract methods in a class that can be declared as abstract classes to prevent class instantiation.

Abstract class Preson {public abstract function setInfo (); / / Abstract method public function getInfo () {echo "get information";}} new Preson; / / error. Abstract class cannot instantiate / / inherit class Student extends Preson {public function setInfo () {echo "re-implement the abstract method of the parent class";}}

The role of an abstract class:

1. Define naming conventions

two。 Prevent instantiation, if a class is full of static methods, then the class does not need to be instantiated, you can use the abstract keyword to prevent instantiation

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