PHP Classes and Objects – Build the Blueprint and Instances of Your Application

Learn how to define and use classes and objects in PHP, the foundation of object-oriented programming (OOP).

Introduction – What Are Classes and Objects?

In PHP OOP, a class is a blueprint that defines the structure and behavior of an object, while an object is an instance of that class containing actual data and the ability to perform defined actions.

In this guide, you’ll learn:

• How to define a PHP class
• How to create and use an object
• How to define and access properties and methods
• Real-world examples and best practices

1. Defining a Class

class Car {
    public $brand;

    public function honk() {
        echo "Beep beep!";
    }
}

A class is defined using the class keyword.
It can contain properties (variables) and methods (functions).

2. Creating an Object (Instance)

$car = new Car();
$car->brand = "Toyota";
echo $car->brand; // Toyota

Use new ClassName() to create an object.
Use -> to access or modify properties and methods.

3. Adding a Constructor Method

class Car {
    public $brand;

    public function __construct($brand) {
        $this->brand = $brand;
    }

    public function honk() {
        echo "Beep! I'm a $this->brand.";
    }
}

$car = new Car("Honda");
$car->honk(); // Beep! I'm a Honda.

__construct() is called automatically when the object is created.
$this refers to the current object instance.

4. Class Properties and Methods

class User {
    public $name;

    public function greet() {
        echo "Hello, $this->name!";
    }
}

$user = new User();
$user->name = "Alice";
$user->greet(); // Hello, Alice!

Properties hold object data.
Methods define object behavior.

5. Property Visibility: public, private, protected

class Account {
    private $balance = 100;

    public function getBalance() {
        return $this->balance;
    }
}

$acc = new Account();
// echo $acc->balance; //  Error
echo $acc->getBalance(); //  100

private limits access to inside the class only.
Use getter/setter methods to safely access private properties.

Best Practices

• Use __construct() to initialize objects
• Encapsulate data using private and protected visibility
• Name classes with PascalCase and methods/properties with camelCase
• Don’t access or modify properties directly unless they’re public
• Keep class responsibilities focused (Single Responsibility Principle)

Summary – Recap & Next Steps

Classes and objects form the core of OOP in PHP. A class defines structure and behavior, and an object uses that blueprint to store data and perform actions.

Key Takeaways:

• Classes are blueprints; objects are instances of them
• Properties store data; methods define behavior
• Constructors automatically run on object creation
• Use $this to refer to the current object

Real-World Use Cases:
Users, products, orders, carts, articles, vehicles, form builders, authentication systems.

Frequently Asked Questions (FAQs)

Can I create multiple objects from the same class?
Yes! Each object is independent and has its own data.

What is the difference between $this->property and $object->property?
$this->property is used inside the class; $object->property is used externally.

Can I create a class inside a function?
Technically yes, but it’s not common or recommended.

Do I always need a constructor?
No, but it’s helpful for initializing object values.

Can a method return $this?
Yes — it supports method chaining (e.g., $obj->set()->save()).