Please watch: "oops concepts in php in hindi"
https://www.youtube.com/watch?v=35AjG2TehuM
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This is popular feature of php oops programming. Abstract classes are important for many purposes like you can hide data at the same time you can also achieve inheritance.
Abstract classes are normally like php classes the only difference is that you can not create an instance of the abstract classes.
Abstract classes act like a Base classes for other child classes. You can define properties and abstract methods inside a class
You can define all the access layers like public protected and private inside a abstract class
When one define a abstract method inside a abstract class you can just declare the definition of it. it's declaration is implemented in the child class
