Object-oriented programming in PHP

Object-oriented programming (OOP) in PHP is a powerful way to structure and manage your code. Here’s a basic introduction to help you get started:

1. Classes and Objects

Classes are blueprints for objects. They define properties (variables) and methods (functions) that the objects created from the class will have.

<?php
class Car {
    public $color; // Property
    public $model;

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

    // Method
    public function getDetails() {
        return "This is a $this->color $this->model.";
    }
}

// Creating an object
$myCar = new Car("red", "Toyota");

// Accessing a method
echo $myCar->getDetails();
?>

2. Properties and Methods

Properties: Variables that belong to a class.
Methods: Functions that belong to a class.

<?php
class Person {
    public $name; // Property
    private $age; // Private property

    // Method
    public function setName($name) {
        $this->name = $name;
    }

    // Private Method
    private function setAge($age) {
        $this->age = $age;
    }
}

$person = new Person();
$person->setName("John Doe");
echo $person->name; // Outputs: John Doe
?>

3. Visibility

public: Accessible from anywhere.
private: Accessible only within the class.
protected: Accessible within the class and by inheriting classes.

<?php
class Example {
    public $publicVar = "I am public";
    private $privateVar = "I am private";
    protected $protectedVar = "I am protected";

    public function showVariables() {
        echo $this->publicVar;
        echo $this->privateVar;
        echo $this->protectedVar;
    }
}

$example = new Example();
echo $example->publicVar; // Works
// echo $example->privateVar; // Fatal error
// echo $example->protectedVar; // Fatal error
?>

4. Inheritance

Inheritance allows a class to use the properties and methods of another class.

<?php
class Animal {
    public $name;

    public function speak() {
        echo "Animal sound";
    }
}

class Dog extends Animal {
    public function speak() {
        echo "Woof! Woof!";
    }
}

$dog = new Dog();
$dog->speak(); // Outputs: Woof! Woof!
?>

5. Interfaces

Interfaces allow you to define methods that must be implemented in any class that implements the interface.

<?php
interface Shape {
    public function area();
}

class Circle implements Shape {
    private $radius;

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

    public function area() {
        return pi() * $this->radius * $this->radius;
    }
}

$circle = new Circle(5);
echo $circle->area(); // Outputs the area of the circle
?>

6. Abstract Classes

Abstract classes cannot be instantiated and are meant to be extended by other classes. They can have both abstract and concrete methods.

<?php
abstract class Vehicle {
    abstract public function startEngine();

    public function honk() {
        echo "Honk! Honk!";
    }
}

class Car extends Vehicle {
    public function startEngine() {
        echo "Car engine started";
    }
}

$car = new Car();
$car->startEngine(); // Outputs: Car engine started
$car->honk(); // Outputs: Honk! Honk!
?>

7. Traits

Traits are a mechanism for code reuse in single inheritance languages like PHP. They allow you to include methods in multiple classes.

<?php
trait Logger {
    public function log($message) {
        echo "Log: $message";
    }
}

class Application {
    use Logger;
}

$app = new Application();
$app->log("Application started"); // Outputs: Log: Application started
?>

8. Namespaces

Namespaces are a way to encapsulate items to avoid name conflicts.

<?php
namespace MyApp;

class User {
    public function __construct() {
        echo "User class from MyApp namespace";
    }
}

$user = new \MyApp\User();
?>

Practice and Resources
Practice: Write small programs using these concepts to get comfortable with OOP in PHP.
Resources:

• PHP Manual on Classes and Objects
• Object-Oriented PHP for Beginners
• PHP: The Right Way

By understanding and practicing these concepts, you’ll be well on your way to mastering OOP in PHP.