Object Oriented Programming in PHP

Question 1

Q: What is Object-Oriented Programming (OOP)?

Answer 1

A: A programming paradigm based on the concept of objects, which encapsulate data and behaviour.

Question 2

Q: What are the four main principles of OOP?

Answer 2

A: Encapsulation, Inheritance, Polymorphism, and Abstraction.

Question 3

Q: How do you define a class in PHP?

Answer 3

class ClassName {
// Class properties and methods
}

Question 4

Q: How do you create an object in PHP?

Answer 4

$object = new ClassName();

Question 5

Q: What is a property in a PHP class?

Answer 5

A: A variable defined within a class to hold data.

Question 6

Q: What are the three access modifiers in PHP?

Answer 6

A: public, protected, and private.

Question 7

Q: What does the public access modifier mean?

Answer 7

A: The property or method is accessible from anywhere.

Question 8

Q: What does the protected access modifier mean?

Answer 8

A: The property or method is accessible within the class and its subclasses.

Question 9

Q: What does the private access modifier mean?

Answer 9

A: The property or method is accessible only within the class.

Question 10

Q: How do you define a private property in PHP?

Answer 10

private $propertyName;

Question 11

Q: What is a method in a PHP class?

Answer 11

A: A function defined within a class to perform actions.

Question 12

Q: How do you define a method in PHP?

Answer 12

public function methodName() {
// Code
}

Question 13

Q: How do you call a method of a class?

Answer 13

$object->methodName();

Question 14

Q: What is the $this keyword in PHP?

Answer 14

A: A reference to the current object instance.

Question 15

Q: Can methods have arguments in PHP?

Answer 15

A: Yes, just like regular functions.

Question 16

Q: What is a constructor in PHP?

Answer 16

A: A special method automatically called when an object is instantiated.

Question 17

Q: What is the syntax for defining a constructor in PHP?

Answer 17

public function __construct() {
// Initialization code
}

Question 18

Q: What is a destructor in PHP?

Answer 18

A: A special method called when an object is destroyed or the script ends.

Question 19

Q: What is the syntax for defining a destructor in PHP?

Answer 19

public function __destruct() {
// Cleanup code
}

Question 20

Q: Can constructors have arguments in PHP?

Answer 20

A: Yes, arguments can be passed during object creation.

Question 21

Q: What is inheritance in OOP?

Answer 21

A: A mechanism where a class can inherit properties and methods from another class.

Question 22

Q: How do you extend a class in PHP?

Answer 22

class ChildClass extends ParentClass {
// Additional properties and methods
}

Question 23

Q: What is the parent keyword used for?

Answer 23

A: To call a parent class’s method or constructor.

Question 24

Q: What is method overriding in PHP?

Answer 24

A: Redefining a parent class’s method in a child class.

Question 25

Q: Can private properties be inherited?

Answer 25

A: No, private properties are not accessible in child classes.

Question 26

Q: What is polymorphism in OOP?

Answer 26

A: The ability to use the same method name with different implementations in derived classes.

Question 27

Q: How is polymorphism achieved in PHP?

Answer 27

A: Through method overriding.

Question 28

Q: What is the purpose of the final keyword in PHP?

Answer 28

A: To prevent a class from being extended or a method from being overridden.

Question 29

Q: What is an abstract class in PHP?

Answer 29

A: A class that cannot be instantiated and may contain abstract methods.

Question 30

Q: What is an abstract method in PHP?

Answer 30

A: A method declared in an abstract class but not implemented.

Question 31

Q: What is an interface in PHP?

Answer 31

A: A blueprint for classes that defines methods a class must implement.

Question 32

Q: How do you define an interface in PHP?

Answer 32

interface InterfaceName {
public function methodName();
}

Question 33

Q: How do you implement an interface in a class?

Answer 33

class ClassName implements InterfaceName {
public function methodName() {
// Implementation
}
}

Question 34

Q: Can a class implement multiple interfaces in PHP?

Answer 34

A: Yes, a class can implement multiple interfaces.

Question 35

Q: What is the difference between an abstract class and an interface?

Answer 35

A: An abstract class can have implemented methods, while an interface cannot.

Question 36

Q: What is the static keyword in PHP?

Answer 36

A: Used to define properties or methods that belong to the class, not instances.

Question 37

Q: How do you access a static method in PHP?

Answer 37

ClassName::staticMethod();

Question 38

Q: What is a trait in PHP?

Answer 38

A: A mechanism for reusing methods across multiple classes.

Question 39

Q: How do you include a trait in a class?

Answer 39

class ClassName {
use TraitName;
}

Question 40

Q: Can you use multiple traits in a class?

Answer 40

A: Yes, a class can use multiple traits.