Interview Questions and Answers - Object Orient Programming in PHP (OOP) - Basics

Question.1. 
what is class?

Answer: 

• Its a blue print (Technical Design/structure) of how methods & behaviors will be written/shown. 

Question.2:
What is an object?

Answer:

• Its an instance of a class.

Question.3.
What is the Interface?
Answer:

• functionality cannot be provided
• properties cannot be defined
• it is to enforce child class to implement all the methods existing in interface is a MUST. 
• it cannot be instantiated. 
• methods can only be public inside interface.
• child class can only implement not extend with interface
• every method should be abstracted 
• multiple inheritance is possible with implements keyword
• multi-level inheritance is possible , that is an interface can extend parent interface and a class can implement child interface and it should implement all the methods from parents interfaces.

Question 4:
What is an Abstract class?

Answer:

• functionality can be provided inside it
• properties can be defined inside it
• Methods cannot be private, 
• child class must implement abstract methods
• child class can extend an abstract class with "extends" keyword instead of "implements" 
• not every method should be abstract
• multiple inheritance is not possible

Question 5:

What are properties?

Answer:

• information / data/state of an object

Question 6:
What is are Methods?

Answer:

• Functions or behaviors of the class

Question 7:
What is Encapsulation?

Answer:

• to enclose the properties and behaviors in curly braces so that we don't need to know the information processing inside a class while working with an API calls to this class.

Question 8:
What are Visibility/Access Modifiers?
Answer:

• Public - accessible from everywhere
• Protected - accessible from within class as well child classes
• private  - accessible from within class ONLY 

Question 9:
What is Static?

Answer:

• Method or property available at class level , no object needed
• changes will affect everywhere in all the instances of the class

Question 10:
What is Constructor?

Answer:

• Its a magic method
• used to initialize the properties of an object 

Question: 11:

What is Polymorphism:

Answer:

Its a concept that an object can have different forms, means a class can have many child classes which are related to parent class but having different behaviors.

example:

interface Speaking{

     public function speak();

}

cat implements speaking{

     

     public function speak(){

           echo 'meeaoo';

     }

}

dog implements speaking{

     

     public function speak(){

           echo 'woooah';

     }

}

person implements speaking{

     

     public function speak(){

           echo 'lets go';

     }

}