PHP Classes | Basics of OOP Programming

Object-oriented programming (OOP) allows us to organize code around real-world things (objects). A class is a blueprint (e.g., a car blueprint), while an object is a concrete thing made according to that blueprint (e.g., your car parked in front of the house).

EXAMPLE

[file:Base Class and Constructor]
<?php
/**
 * Car class with basic public properties.
 */
class Car {
    public $brand;
    public $model;
    public $year;

// The constructor executes automatically when an object is created
    public function __construct($brand, $model, $year) {
        $this->brand = $brand;
        $this->model = $model;
        $this->year = $year;
    }

public function displayData() {
        return "Vehicle: {$this->brand} {$this->model} ({$this->year})";
    }
}

// Creating an instance (object)
$myCar = new Car("Toyota", "Corolla", 2020);
echo $myCar->displayData();
?>

[file:Encapsulation (Getters and Setters)]
<?php
/**
 * Using private properties for better data security.
 */
class ProCar {
    private $brand;
    private $year;

public function __construct($brand, $year) {
        $this->brand = $brand;
        $this->setYear($year); // We use the setter right inside the constructor!
    }

// Setter with logical validation (PRO approach)
    public function setYear($year) {
        $currentYear = date("Y");
        if ($year > 1885 && $year <= $currentYear) {
            $this->year = $year;
        } else {
            $this->year = "Unknown";
        }
    }

public function getYear() {
        return $this->year;
    }

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

$car = new ProCar("Honda", 2024);
echo "Brand: " . $car->getBrand() . ", Year: " . $car->getYear();
?>

[file:Static Elements (Statics)]
<?php
/**
 * Static elements belong to the class, not to an individual object.
 */
class Garage {
    public static $garageNumber = "A-101";
    public static $vehicleCount = 0;

public function __construct() {
        self::$vehicleCount++; // Increase the counter with each new car
    }

public static function displayStatus() {
        return "In garage " . self::$garageNumber . " there are currently: " . self::$vehicleCount . " vehicles.";
    }
}

$c1 = new Garage();
$c2 = new Garage();

// Static methods are accessed using the scope resolution operator (::)
echo Garage::displayStatus(); 
?>

[file:Constants Inside a Class]
<?php
class Specification {
    // Constants are always public and do not change
    const FUEL_TYPE = "Petrol";

public function showFuel() {
        return "This vehicle uses: " . self::FUEL_TYPE;
    }
}

$spec = new Specification();
echo $spec->showFuel();
?>

RESULT

The result will be displayed here...

OOP Basics: Classes