In PHP, Object-Oriented Programming (OOP) makes it easier to organize and reuse code. The two fundamental building blocks in OOP are classes and objects.
PHP Classes
A class in PHP is a blueprint for creating objects. It defines the properties (variables) and methods (functions) that the objects created from the class will have. By using classes, we can group related data and actions, making it easier to organize and manage our code.
In PHP, a class is defined using the class keyword, followed by the class name and curly braces.
Syntax:
<?php class Cars { // PHP code goes here... } ?>Now, let us understand with the help of the example:
PHP <?php class Car { public $brand, $model, $year; function __construct($brand, $model, $year) { $this->brand = $brand; $this->model = $model; $this->year = $year; } function displayInfo() { echo "$this->brand $this->model, $this->year"; } } $car = new Car("Toyota", "Corolla", 2021); $car->displayInfo(); ?> OutputToyota Corolla, 2021
In this example:
- The Car class is defined with three properties: $brand, $model, and $year.
- The __construct() method initializes the properties when a new object of the Car class is created, using the provided values.
- The displayInfo() method is defined to print out the car's brand, model, and year.
- A new object $car is created from the Car class, and values ("Toyota", "Corolla", 2021") are passed to the constructor.
- The displayInfo() method is called on the $car object to display the car's details: "Toyota Corolla, 2021".
To read more about PHP classes refer this article - PHP Classes
PHP Objects
An object is an instance of a class. When you create an object from the class, memory is allocated, and the object can store data and perform actions defined in the class. To create an object, we use the new keyword.
Syntax:
$objectName = new ClassName($value);
Now, let us understand with the help of the example:
PHP <?php class Car { public $brand; function __construct($brand) { $this->brand = $brand; } function displayInfo() { echo "Car brand: $this->brand"; } } $myCar = new Car("Toyota"); $myCar->displayInfo(); // Output: Car brand: Toyota ?> In this example:
- The Car class has one property, $brand, and a method displayInfo() to display the car's brand.
- An object $myCar is created from the Car class with the brand "Toyota".
- The displayInfo() method is called to show the car's brand.
To read more about PHP Objects refer this article - PHP Objects
Using the $this Keyword
In PHP, the $this keyword is used within a class to refer to the current object. It allows you to access properties and methods of the current object from within the class.
Now, let us understand with the help of the example:
PHP <?php class Car { public $brand; public $model; // Constructor to initialize properties public function __construct($brand, $model) { $this->brand = $brand; // Accessing current object property $this->model = $model; // Accessing current object property } // Method to display information public function displayInfo() { echo "Car Brand: $this->brand, Model: $this->model"; } } $myCar = new Car("Toyota", "Corolla"); $myCar->displayInfo(); ?> OutputCar Brand: Toyota, Model: Corolla
In this example:
- $this->brand refers to the brand property of the current object ($myCar).
- $this->model refers to the model property of the current object.
- The displayInfo() method uses $this to access the properties of the object and display them.
Why Use Classes and Objects?
- Code Reusability: Classes allow you to define functionality once and reuse it across multiple objects, reducing code duplication.
- Flexibility: Inheritance and polymorphism allow you to extend and modify functionality easily without rewriting code.
- Maintainability: Classes make it easier to update and expand your code because changes are limited to specific parts of the code (the class) rather than affecting everything.
Conclusion
PHP classes and objects are essential tools for organizing and managing code in an object-oriented way. A class acts as a blueprint for creating objects, while an object is an instance of that class. The $this keyword helps access an object's properties. By understanding these concepts, you can create more flexible, reusable, and organized PHP code.