When we use abstract class

[system]

Hi,

I am php cms developer.I want to know exactly when abstract class are used in cms like WordPress , Drupal and php framework like codeigniter.Where we are exactly using using abstract class.In interview many interviewer ask this question when you are using abstract class or in your project
Where you used abstract class.please help me understand this topic of abstraction and their uses.

Regards
Chitrasen

[astonecipher]

https://www.developer.com/lang/php/article.php/3604111/PHP-5-OOP-Interfaces-Abstract-Classes-and-the-Adapter-Pattern.htm