Object-Oriented Programming (OOP) organises code around objects — instances of classes that bundle data (properties) and behaviour (methods) together. A class is the blueprint; an object is the instance.
class keyword.new ClassName().-> arrow operator.<?php
class Product
{
// Properties (typed since PHP 7.4)
public string $name;
public float $price;
public int $stock;
// Constructor
public function __construct(string $name, float $price, int $stock = 0)
{
$this->name = $name;
$this->price = $price;
$this->stock = $stock;
}
// Method
public function totalValue(): float
{
return $this->price * $this->stock;
}
public function isInStock(): bool
{
return $this->stock > 0;
}
public function describe(): string
{
return sprintf(
'%s — $%.2f (%d in stock)',
$this->name,
$this->price,
$this->stock
);
}
}
// Instantiate
$widget = new Product('Widget', 9.99, 50);
$gadget = new Product('Gadget', 49.99);
echo $widget->describe(); // Widget — $9.99 (50 in stock)
echo $widget->totalValue(); // 499.5
echo $gadget->isInStock() ? 'In stock' : 'Out of stock'; // Out of stock
// Multiple independent instances
$a = new Product('Alpha', 1.00, 10);
$b = new Product('Beta', 2.00, 5);
echo $a->name; // Alpha
echo $b->name; // Beta — separate objects
Tip: In PHP 8.0+ you can use constructor property promotion to declare and assign properties in one line: public function __construct(public string $name, public float $price) {} — no need to repeat the property declarations above the constructor.