Object-oriented programming (OOP) is a fundamental part of PHP development, and interviewers often focus on its concepts. A strong grasp of classes, objects, inheritance, and polymorphism can make a real difference. This guide compiles 20 PHP OOPs interview questions and answers for 2025, covering key topics in a clear and practical way.
Use it to sharpen your knowledge and approach your next interview with confidence.
Fun Fact: PHP developer salaries in India range from ₹1.1 lakh to ₹6.8 lakhs for those with 1 to 6 years of experience.
PHP OOPs Interview Questions for Freshers
Here is a list of common OOPs interview questions and answers in PHP for freshers:
- What is Object-Oriented Programming (OOP) in PHP?
Object-Oriented Programming (OOP) is a programming approach that organizes code into objects and classes. Objects are instances of classes, which contain properties (variables) and methods (functions). OOP allows for better code organization, modularity, and reusability.
- What are the main principles of OOP?
The four core OOP principles are:
- Encapsulation: Restricting direct access to object data and exposing only necessary parts through methods.
- Abstraction: Hiding implementation details and exposing only essential features.
- Inheritance: Allowing a class to inherit methods and properties from another class.
- Polymorphism: Allowing objects to take multiple forms, enabling method overriding or interfaces.
- How do classes and objects differ in PHP?
- Class: A blueprint defining properties and methods but does not allocate memory.
- Object: An instance of a class that occupies memory and can perform operations.
Example:
class Car {
public $brand;
public function drive() {
echo “Driving”;
}
}
$myCar = new Car(); // Object of Car class
- What is inheritance in PHP?
Inheritance allows a child class to access the properties and methods of a parent class. This reduces code duplication and fosters a hierarchical relationship between classes. For example, a Vehicle class with move() can be inherited by Car and Bike classes, which extend the method’s functionality.
- Can you explain polymorphism with an example in PHP?
Polymorphism allows different classes to have methods with the same name but different implementations. This helps create flexible and scalable applications by letting objects of different types be treated uniformly when calling the same method.
Example:
interface Shape {
public function area();
}
class Circle implements Shape {
private $radius;
public function __construct($radius) {
$this->radius = $radius;
}
public function area() {
return 3.14 * $this->radius * $this->radius;
}
}
class Square implements Shape {
private $side;
public function __construct($side) {
$this->side = $side;
}
public function area() {
return $this->side * $this->side;
}
}
Object Oriented PHP Interview Questions for Experienced
Let’s go through some important PHP OOPs interview questions and answers for experienced candidates:
- How does PHP implement encapsulation?
Encapsulation is implemented using access modifiers (public, private, protected). Private properties are accessible only within the class, and public properties are accessible from anywhere.
Example:
class User {
private $password;
public function setPassword($password) {
$this->password = $password;
}
public function getPassword() {
return $this->password;
}
}
- What are interfaces in PHP, and how are they used?
An interface defines a set of method signatures that implementing classes must follow. Unlike abstract classes, interfaces cannot have properties or method implementations, enforcing strict adherence to a contract among multiple classes.
- Can you explain the concept of traits in PHP?
Traits allow code reuse when multiple classes need the same functionality but cannot use inheritance due to PHP’s single-inheritance constraint. Traits solve this by allowing methods to be shared across different classes.
- How does PHP handle method overloading?
PHP does not support traditional method overloading (multiple functions with the same name but different parameters). However, it allows handling undefined method calls using the __call() magic method, making it possible to define flexible method behavior dynamically.
Example:
class Test {
public function __call($name, $arguments) {
echo “Method $name does not exist!”;
}
}
$obj = new Test();
$obj->undefinedMethod(); // Output: Method undefinedMethod does not exist!
PHP OOPs Interview Questions for 5 Year Experienced
These are commonly-asked PHP OOPs interview questions and answers for 5 year experienced candidates:
- What are abstract classes in PHP, and when would you use them?
Abstract classes define a common structure for multiple related classes but cannot be instantiated. They allow defining methods that must be implemented in child classes while providing a shared foundation for related objects.
Example:
abstract class Animal {
abstract public function makeSound();
}
class Dog extends Animal {
public function makeSound() {
return “Bark”;
}
}
Use abstract classes when you want to enforce certain methods while allowing flexibility in implementation.
- How do you implement design patterns like Singleton or Factory in PHP?
A Singleton pattern guarantees that only one instance of a class exists throughout the application lifecycle. The Factory pattern creates objects dynamically, providing flexibility when object instantiation logic needs to be managed externally.
Example:
class Singleton {
private static $instance;
private function __construct() {}
public static function getInstance() {
if (!self::$instance) {
self::$instance = new Singleton();
}
return self::$instance;
}
}
PHP OOPs Interview Questions for 7 Years Experienced
- How do you optimize the performance of PHP applications using OOP principles?
- Use autoloading to load classes dynamically.
- Minimize deep inheritance to reduce complexity.
- Use dependency injection to avoid tightly coupled classes.
- Optimize database queries when using ORM.
- Can you discuss the impact of OOP design on application scalability and maintenance?
A well-structured OOP design simplifies feature expansion, debugging, and long-term maintenance. By organizing code into reusable, modular components, OOP reduces redundancy and ensures that modifications affect only relevant parts of the system.
PHP OOPs Concepts Interview Questions
You might also come across OOPs concepts in PHP interview questions like these:
- What is the difference between composition and inheritance in PHP?
- Inheritance: One class extends another (is-a relationship).
- Composition: One class contains another (has-a relationship).
Example of Composition:
class Engine {}
class Car {
private $engine;
public function __construct() {
$this->engine = new Engine();
}
}
- How does PHP support multiple inheritance?
PHP does not support multiple inheritance directly. Instead, traits allow code reuse across multiple classes without using inheritance, solving the limitation.
- What is the role of the __construct() method in PHP?
The __construct() method is a special function called automatically when an object is created. It initializes class properties or performs setup tasks, reducing the need for manual initialization.
Example:
class Car {
public function __construct($brand) {
echo “Car brand: ” . $brand;
}
}
$newCar = new Car(“Toyota”);
- Can you explain the concept of late static binding in PHP?
Late static binding refers to the ability to reference the calling class rather than the parent class. It is useful when working with inheritance and static methods, guaranteeing that method calls execute in the correct class context.
Example:
class ParentClass {
public static function getClassName() {
return static::class;
}
}
class ChildClass extends ParentClass {}
echo ChildClass::getClassName(); // Outputs: ChildClass
Advanced OOPs Interview Questions PHP
Here is a list of advanced PHP OOPs interview questions and answers:
- How do namespaces work in PHP, and why are they important?
Namespaces prevent class name conflicts when using multiple libraries or frameworks. They group logically related classes under a unique name, ensuring cleaner and more manageable code structures.
Example:
namespace App\Controllers;
class UserController {}
- What are magic methods in PHP, and how do they function?
Magic methods start with __ and provide special behaviors.
Example:
class Test {
public function __toString() {
return “This is a Test class”;
}
}
$obj = new Test();
echo $obj; // Calls __toString()
- Can you explain the concept of dependency injection in PHP?
Dependency injection allows passing dependencies from outside rather than creating them inside the class. This promotes loose coupling and makes unit testing easier, as dependencies can be swapped without modifying core logic.
Example:
class Database {
private $connection;
public function __construct(Connection $connection) {
$this->connection = $connection;
}
}
Also Read - Top 25+ Python OOPs Interview Question (2025)
Wrapping Up
These 20 PHP OOPs interview questions and answers cover essential concepts to help you prepare for your next technical interview. Understanding these topics will improve your coding skills and problem-solving abilities. If you are looking for PHP OOPs jobs in India, Hirist is the right platform. Find top tech job opportunities and advance your career today.