PHP Classes and Objects

Classes and Objects are the two main aspects of object-oriented programming. A **Class** acts as a blueprint or a template, while an **Object** is an individual instance created from that blueprint.

1. What is a Class?

A class is a user-defined data type. It defines the structure of the data and the functions that can operate on that data. Think of a class as a blueprint for a house. It shows where the walls, doors, and windows should be, but it isn't a house itself.

Defining a Class

You define a class using the class keyword followed by the name of the class.

<?php
    class Fruit {
        // Properties and methods go here
    }
?>

2. Properties and Methods

Inside a class, you define variables (called **Properties**) and functions (called **Methods**).

• Properties: Variables that hold data about the object.
• Methods: Functions that define what the object can do.

<?php
    class Fruit {
        // Properties
        public $name;
        public $color;

        // Methods
        function set_name($name) {
            $this->name = $name;
        }
        function get_name() {
            return $this->name;
        }
    }
?>

3. What is an Object?

An object is an instance of a class. If the class is the blueprint, the object is the actual house built from that blueprint. You can create many objects from a single class, and each object can have its own data.

Instantiating an Object

You create an object using the new keyword.

<?php
    // Instantiate the object
    $apple = new Fruit();
    $banana = new Fruit();

    // Access properties and methods using ->
    $apple->set_name('Apple');
    $banana->set_name('Banana');

    echo $apple->get_name(); // Outputs: Apple
    echo $banana->get_name(); // Outputs: Banana
?>

Key Differences

Using the instanceOf Keyword

You can check if an object belongs to a specific class using the instanceof keyword. This is very useful for validation.

<?php
    $apple = new Fruit();
    var_dump($apple instanceof Fruit); // Outputs: bool(true)
?>

Summary

• A Class is a template for objects.
• An Object is a specific instance of a class.
• Use the class keyword to define a class.
• Use the new keyword to create an object.
• Use -> (arrow operator) to access properties and methods of an object.