PHP Oops Interview Questions

Here you can get PHP oops interview questions. What is Object-Oriented Programs (OOP) and How We can relate All these by Programs?
Object means in real-life Sun, Moon, House, Vehicle, Computer, Books, Home appliance, etc. Here let an example of a house is made of by Bricks, Sand, Iron Rod, and Cement as these all are an object, so taking all to a make a house. Same way Software made of different Object.

In Software Object-Oriented Programs (OOP) are having different terms. Before going to interview OOPs in PHP interview questions answers you should first to gain some knowledge regarding OOps.

Class
Object
Member Variable
Member Function
Inheritance
Keywords(Public,Private,Protected,etc)
Encapsulation
Constructor
Destructor
Overloading
Parent Class
Child Class
Data Abstraction
Polymorphism
Interface
Constants

So If we know all those thoroughly their behavior and uses then we can use that Oops concept in our program.
Then Why you will use object Oriented Concept in your Program. What is the advantages of Oops in PHP?

Code Readable
Code Reusable
Code Structured
Time Saving
Better performance

Table of Contents

1. What is a class concept oop in PHP?
What is an object in oop in PHP?
What are the basic difference between class and object in PHP
What is inheritance in oop PHP
Why multiple inheritances not supported in PHP and how we can achieve this?
What is interface explain with example?
What is the difference between Abstract class and Interface?
What is access modifier?
What is the use of the final keyword in PHP oop?
What is the Concept of Abstraction in PHP?

1. What is a class concept oop in PHP?

Class is a programmer-defined data type which is consist of properties and methods.
It’s a blueprint of an object.
It defines the properties or functionality of an Object.

Example of Class in PHP, Here you need to create a class, the name should be the same as file name.

<?php
class Laptop{
public function Brand(){
echo “Lenovo”;
}
public function price(){
echo “Rs 34000.00”;
}
}
$obj = new Laptop();
$obj->Brand();
$obj->price();
?>

//Output
Lenovo
Rs 34000.00

<?php

class Laptop{

public function Brand(){

echo “Lenovo”;

}

public function price(){

echo “Rs 34000.00”;

}

$obj = new Laptop();

$obj->Brand();

$obj->price();

//Output

Lenovo

Rs 34000.00

What is an object in oop in PHP?

An object is an instance of a class.
An object can instantiate, but a class can’t instantiate.
new is a keyword to Instantiate an object of a class.

Above an example, you can see the class name Laptop and object is created by using keyword new. see the example below.

$obj = new Laptop();

1	$obj = new Laptop();

What are the basic difference between class and object in PHP

Class-
1. Class is a blueprint of an object.
2. A class can’t instantiate.
4. Class is generic.
Object-
1. An object is an instance of a class.
2. An object can instantiate.
4. Object is specific.

What is inheritance in oop PHP

If child class can access the methods or variables of it’s parent class then you can call that is inheritance.However the parent class property or methods should be public or protected,so it can inherited.
Here PHP supports single level inheritance and multilevel inheritance but not supports multiple inheritance.
Inheritance in oop PHP done by keywords. extends

<?php

class A{

function Developer(){
echo "PHP Developer";
}
}

class B extends A{
}

$b= new B();
$b->Developer(); // PHP Developer.

?>

<?php

class A{

function Developer(){

echo "PHP Developer";

}

class B extends A{

}

$b= new B();

$b->Developer(); // PHP Developer.

Why multiple inheritances not supported in PHP and how we can achieve this?

Multiple inheritances suffer from the Diamond Problem, which has not been solved in PHP yet, so to overcome it PHP provides the interface. By using multiple interfaces we can achieve the same as multiple inheritances.

What is interface explain with example?

1. Interfaces contain no data variables, only function prototypes.
2. Abstract classes and interface both are same but the only difference is abstract classes this is not necessary that every method should be abstract. But in interface every method is abstract.
3. The interface you can only define your methods without the body.
4. It can create by using the keyword interface.
5. It used in a class to simulate multiple inheritances the keyword implements.
6. A class can implement multiple interfaces.

Examples-
interface Interface_name{
public some_function();
}
Class A implements Interface_name{
public some_function(){
// Body must be here.
echo "I am a PHP developer.";
}
$b= new A();
$b->some_function(); // Output : I am a PHp developer.

Examples-

interface Interface_name{

public some_function();

}

Class A implements Interface_name{

public some_function(){

// Body must be here.

echo "I am a PHP developer.";

}

$b= new A();

$b->some_function(); // Output : I am a PHp developer.

Example of implementation of multiple interfaces in one single class.

interface One { }
interface Two { }
interface Three { }
//A class can implements multiple interfaces
class A implements One, Two, Three { }

interface One { }

interface Two { }

interface Three { }

//A class can implements multiple interfaces

class A implements One, Two, Three { }

What is the difference between Abstract class and Interface?

Interface:
1. The interface supports multiple inheritances.
2. Interface methods do not contain any body.
3. The interface does not contain any data member.
4. All methods of an interface must be defined as public.
Abstract Class:
1. Abstract class never support multiple inheritances.
2. Abstract class methods contain the body.
3. abstract class contains data member.
4. Methods and members of an abstract class can be defined with any visibility.

What is access modifier?

It’s a very important feature in the object-oriented program, it provides visibility of methods or property of a class. There are 3 types of access modifiers available. these follow below:
1.Private.
2. Protected.
3.Public.

What is the use of the final keyword in PHP oop?

Final is a keyword which prevents child classes from overriding a method. If you pre-fix the final keyword before a class it can’t be extendable by another class.

What is the Concept of Abstraction in PHP?

Abstraction is a key feature in PHP, in which you can restrict a class for creating an object. If you pre-fix this keyword abstract then it can’t create an instance.

abstract class A

{ // Body

}

abstract class A

{ // Body

}

In above class A, you can not able to create an object or instance but you only extend it by using keyword. extends.