Learn PHP Programming

<?php
declare(strict_types=1);

class Product {
    // Typed properties (PHP 7.4+)
    private string $name;
    private float $price;
    private int $quantity;
    private string $sku;

    public function __construct(
        string $name,
        float $price,
        int $quantity = 0,
        string $sku = ''
    ) {
        if ($price < 0) {
            throw new \InvalidArgumentException('Price cannot be negative');
        }
        $this->name = $name;
        $this->price = $price;
        $this->quantity = $quantity;
        $this->sku = $sku;
    }

    // Getter methods
    public function getName(): string { return $this->name; }
    public function getPrice(): float { return $this->price; }
    public function getQuantity(): int { return $this->quantity; }

    // Setter with validation
    public function setQuantity(int $qty): void {
        if ($qty < 0) {
            throw new \InvalidArgumentException('Quantity cannot be negative');
        }
        $this->quantity = $qty;
    }

    // Business logic method
    public function getTotalValue(): float {
        return $this->price * $this->quantity;
    }

    public function applyDiscount(float $percent): void {
        $this->price -= $this->price * ($percent / 100);
    }
}

// Usage
$product = new Product('Laptop', 999.99, 5, 'LAP-001');
echo $product->getName();        // Laptop
echo $product->getTotalValue();  // 4999.95
$product->applyDiscount(10);
echo $product->getTotalValue();  // 4499.96
?>

<?php
class DynamicEntity {
    private array $data = [];

    public function __construct(private string $type) {}

    // Called when accessing inaccessible properties
    public function __get(string $name): mixed {
        return $this->data[$name] ?? throw new \RuntimeException("No property: {$name}");
    }

    // Called when setting inaccessible properties
    public function __set(string $name, mixed $value): void {
        $this->data[$name] = $value;
    }

    // Called when using isset() on inaccessible properties
    public function __isset(string $name): bool {
        return isset($this->data[$name]);
    }

    // Called when object is cast to string
    public function __toString(): string {
        return "{$this->type}: " . json_encode($this->data);
    }
}

$user = new DynamicEntity('User');
$user->name = 'Alice';         // __set
$user->email = 'a@test.com';   // __set
echo $user->name;              // __get → Alice
echo $user;                    // __toString → User: {"name":"Alice","email":"a@test.com"}
?>

<?php
class Address {
    public function __construct(public string $street, public string $city) {}
}

class Customer {
    public function __construct(
        public string $name,
        public Address $address
    ) {}

    // Deep clone nested objects to avoid shared references
    public function __clone(): void {
        $this->address = clone $this->address;
    }
}

$original = new Customer('Alice', new Address('123 Main', 'NYC'));
$copy = clone $original;           // Triggers __clone

$copy->name = 'Bob';
$copy->address->city = 'LA';

echo $original->address->city;    // NYC (deep clone preserved original)
echo $copy->address->city;        // LA

// Comparison operators
$a = new Customer('Alice', new Address('1 St', 'NYC'));
$b = new Customer('Alice', new Address('1 St', 'NYC'));
$c = $a;

var_dump($a == $b);   // true  — same property values
var_dump($a === $b);  // false — different instances
var_dump($a === $c);  // true  — same instance reference
?>

<?php
class DatabaseConfig {
    public function __construct(
        private string $host = 'localhost',
        private int $port = 3306,
        private string $database = 'app',
        private string $charset = 'utf8mb4',
        private bool $persistent = false
    ) {}

    public function getDsn(): string {
        return "mysql:host={$this->host};port={$this->port};" .
               "dbname={$this->database};charset={$this->charset}";
    }
}

// Named arguments: skip defaults, pass in any order
$config = new DatabaseConfig(
    database: 'shop_db',
    persistent: true,
    port: 5432
);
echo $config->getDsn();
// mysql:host=localhost;port=5432;dbname=shop_db;charset=utf8mb4

// Constructor promotion + named args = concise object creation
class Point {
    public function __construct(
        public readonly float $x,
        public readonly float $y,
        public readonly float $z = 0.0
    ) {}
}

$p = new Point(y: 10.5, x: 3.2);
echo "{$p->x}, {$p->y}, {$p->z}";  // 3.2, 10.5, 0.0
?>