PHP Class and Object

Question 1

What is a class in PHP?

Answer 1

A class is a blueprint for creating objects in PHP. It defines properties (attributes) and methods (functions) that the objects created from the class will have. Classes encapsulate data and behavior together.

Question 2

How is an object created in PHP?

Answer 2

An object is created using the new keyword followed by the class name:
$object = new ClassName();

Question 3

What are constructor and destructor in PHP?

Answer 3

Constructor: A special method called automatically when an object is created. It is defined using construct().
Destructor: A special method called automatically when an object is destroyed. It is defined using destruct().

Question 4

What is an interface in PHP?

Answer 4

An interface in PHP is a contract that defines a set of methods that a class must implement. It does not contain any implementation details, only method declarations. Interfaces allow for multiple inheritance, meaning a class can implement multiple interfaces.

Question 5

What is the final keyword in PHP and when is it used?

Answer 5

The final keyword is used to prevent class inheritance or method overriding. When a class is declared as final, it cannot be extended. When a method is declared as final, it cannot be overridden in derived classes.

Question 6

Create a ‘stud’ class in PHP to take RollNo, Name, and MobNo of 10 students and display it back.

Answer 6

class Stud {
public $rollNo;
public $name;
public $mobNo;

public function \_\_construct($rollNo, $name, $mobNo) {
    $this->rollNo = $rollNo;
    $this->name = $name;
    $this->mobNo = $mobNo;
}

public function display() {
    echo "Roll No: $this->rollNo, Name: $this->name, Mobile No: $this->mobNo<br>";
} }

// Create an array to hold student objects
$students = [];
for ($i = 0; $i < 10; $i++) {
$students[] = new Stud(“Roll” . ($i + 1), “Student” . ($i + 1), “123456789” . $i);
}

// Display student details
foreach ($students as $student) {
$student->display();
}

Question 7

What are the different types of visibility (access modifiers) in PHP?

Answer 7

Public: Accessible from anywhere (inside and outside the class).
Protected: Accessible within the class and by derived classes.
Private: Accessible only within the class itself.

Question 8

What is the difference between an abstract class and an interface in PHP?

Answer 8

Abstract Class:
Can have both abstract and concrete methods.
Can have properties and methods with visibility (public, protected, private).
Supports single inheritance.
Interface:
Can only have method declarations (no implementation).
Cannot have properties.
Supports multiple inheritance (a class can implement multiple interfaces).

Question 9

What are the advantages of object-oriented programming (OOP)?

Answer 9

Encapsulation: Bundles data and methods, restricting access to internal states.
Inheritance: Allows classes to inherit properties and methods from other classes, promoting code reuse.
Polymorphism: Enables methods to do different things based on the object