What Are Classes and Objects in PHP

🧱 What Are Classes and Objects in PHP?

Classes and Objects are the core concepts of Object-Oriented Programming (OOP) in PHP.
They help you write clean, reusable, scalable, and real-world structured code.

1️⃣ What is OOP in PHP?

OOP (Object-Oriented Programming) is a programming style where we:

Model real-world entities as objects
Group data + functions together using classes

📌 PHP supports full OOP features since PHP 5+.

2️⃣ What is a Class?

A class is a blueprint or template that defines:

Properties (variables)
Methods (functions)

👉 A class itself does not use memory until an object is created.

Example (Class Definition)

3️⃣ What is an Object?

An object is a real instance of a class.

👉 Objects use memory and can access class properties & methods.

Creating an Object

Output

4️⃣ Real-Life Example ⭐

Real World	OOP
Car	Class
My Car	Object
Color, Speed	Properties
Drive(), Brake()	Methods

5️⃣ `$this` Keyword (Very Important)

$this refers to the current object
Used to access properties & methods inside class

📌 Very common interview question

6️⃣ Class with Constructor ⭐

A constructor runs automatically when an object is created.

<?php
class Student {
public $name;
public $marks;

function __construct($name, $marks) {
$this->name = $name;
$this->marks = $marks;
}

function showDetails() {
echo "Name: $this->name, Marks: $this->marks";
}
}

$s1 = new Student("Ravi", 78);
$s1->showDetails();
?>

<?php

class Student {

public $name;

public $marks;

function __construct($name, $marks) {

$this->name = $name;

$this->marks = $marks;

}

function showDetails() {

echo "Name: $this->name, Marks: $this->marks";

}

$s1 = new Student("Ravi", 78);

$s1->showDetails();

7️⃣ Access Modifiers (Basic Intro)

Modifier	Meaning
`public`	Accessible everywhere
`private`	Only inside class
`protected`	Class + child classes

8️⃣ Class vs Object ⭐ (Interview Favorite)

Feature	Class	Object
Meaning	Blueprint	Instance
Memory	❌ No	✔ Yes
Creation	Once	Multiple
Keyword	`class`	`new`

9️⃣ Why Use Classes & Objects?

✔ Code reusability
✔ Better structure
✔ Easy maintenance
✔ Real-world modeling
✔ Required for frameworks (Laravel, Symfony)

🔟 Common Mistakes ❌

❌ Forgetting new keyword
❌ Not using $this
❌ Confusing class with object
❌ Making everything public

📌 Interview Questions & MCQs

Q1. What is a class?

A) Function
B) Variable
C) Blueprint
D) Object

✅ Answer: C

Q2. What is an object?

A) Blueprint
B) Instance of class
C) Function
D) Variable

✅ Answer: B

Q3. Which keyword creates an object?

A) create
B) object
C) new
D) class

✅ Answer: C

Q4. What does `$this` refer to?

A) Class
B) Method
C) Current object
D) Constructor

✅ Answer: C

Q5. Can a class have multiple objects?

A) Yes
B) No

✅ Answer: A

🔥 Real-Life Use Cases

✔ User management
✔ Product catalog
✔ Bank account systems
✔ MVC frameworks
✔ APIs & enterprise apps

✅ Summary

Class = blueprint
Object = instance of class
Objects access class members using ->
$this refers to current object
Constructors auto-initialize objects
Foundation of PHP OOP & frameworks

What Are Classes and Objects in PHP