Asymmetric Visibility in PHP 8.4: Readonly Scope and Secure Domain Models

Why Public Read, Private Write Matters

In secure enterprise development, ensuring that objects cannot be arbitrarily mutated outside their domain boundaries is paramount. Prior to PHP 8.4, achieving a property that is publicly readable but only writable by the class itself required declaring the property private and implementing a public getter method. PHP 8.4 introduces asymmetric property visibility, allowing developers to set separate visibility scopes for reading and writing.

Syntax: public private(set)

class OrderInvoice {
    public private(set) string $invoiceNumber;
    public private(set) float $totalAmount;
    public private(set) string $paymentStatus;

    public function markAsPaid(string $transactionReference): void {
        $this->paymentStatus = 'PAID';
        // Logging, event dispatching, and audit trail
    }
}

External callers can read $invoice->paymentStatus directly without boilerplate getters, but attempting to execute $invoice->paymentStatus = 'CANCELLED' from outside the class immediately triggers an uncatchable compile-time Error.

Architectural Impact

• Enforces strict immutability in financial ledgers, transactional logs, and compliance records.
• Clean integration with Eloquent and Doctrine ORM hydration pipelines.
• Eliminates defensive cloning and redundant accessor methods.