Classes and Objects in PHP

Introduction to Object-Oriented Programming

Object-Oriented Programming (OOP) is a programming paradigm based on the concept of "objects". Objects are instances of classes, which can hold both data and functions. PHP, being a versatile scripting language, supports OOP, which allows developers to create modular, reusable, and maintainable code.

What is a Class?

A class is a blueprint for creating objects. It defines a set of properties (variables) and methods (functions) that the objects created from the class will have.

class Car {
    public $color;
    public $model;

    public function __construct($color, $model) {
        $this->color = $color;
        $this->model = $model;
    }

    public function getCarDetails() {
        return "This car is a " . $this->color . " " . $this->model;
    }
}
                

Creating an Object

Once a class is defined, you can create objects from it. Each object is an instance of the class and can have its own values for the properties defined in the class.

$myCar = new Car("red", "Toyota");
echo $myCar->getCarDetails();
                

Class Properties and Methods

Properties are variables that belong to a class. Methods are functions that belong to a class. You can access properties and methods of an object using the arrow operator (->).

class Person {
    public $name;
    public $age;

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

    public function introduce() {
        return "Hi, I'm " . $this->name . " and I'm " . $this->age . " years old.";
    }
}

$person = new Person("John", 25);
echo $person->introduce();
                

Access Modifiers

Access modifiers define the visibility of the properties and methods of a class. PHP has three access modifiers: public, protected, and private.

• public: The property or method can be accessed from anywhere.
• protected: The property or method can be accessed within the class and by classes derived from that class.
• private: The property or method can only be accessed within the class.

class Animal {
    private $name;

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

    public function getName() {
        return $this->name;
    }
}

$animal = new Animal("Elephant");
echo $animal->getName();
                

Inheritance

Inheritance is a way to create a new class using an existing class. The new class, known as the child class, inherits properties and methods from the parent class.

class Vehicle {
    public $brand;

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

    public function getBrand() {
        return $this->brand;
    }
}

class Bike extends Vehicle {
    public function message() {
        return "This is a " . $this->getBrand() . " bike.";
    }
}

$bike = new Bike("Honda");
echo $bike->message();