🧱 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()).