Constructors

What it is

A constructor initializes an object; promotion declares and assigns properties.

When to use it

Require valid dependencies and state at creation.

Syntax

public function __construct(private PaymentGateway $gateway) {}

Example

class Checkout
{
    public function __construct(private PaymentGateway $gateway) {}
    public function pay(int $amount): bool
    {
        return $this->gateway->charge($amount);
    }
}

Common mistakes

Avoid network calls in constructors; dependency injection does not require an interface for every class.

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