Property Hooks and Asymmetric Visibility (PHP 8.4)

PHP 8.4 added property hooks: get and set logic attached directly to a property, so you keep simple $obj->prop access while validating or computing values. Asymmetric visibility lets a property be publicly readable but only privately (or protected) writable: public private(set) string $name. Together they remove much getter/setter boilerplate. Virtual properties (hooks without backing storage) compute values on access.

<?php
final class User
{
    public function __construct(
        public private(set) string $email,
        public string $firstName,
        public string $lastName,
    ) {}

    // Virtual property: computed, no storage
    public string $fullName {
        get => "{$this->firstName} {$this->lastName}";
    }

    // Validation on write
    public string $username {
        set(string $value) {
            if (!preg_match('/^[a-z0-9_]{3,20}$/', $value)) {
                throw new InvalidArgumentException('Invalid username');
            }
            $this->username = strtolower($value);
        }
    }

    public function changeEmail(string $email): void { $this->email = $email; }
}

$u = new User('[email protected]', 'Ada', 'Lovelace');
echo $u->fullName;          // Ada Lovelace
// $u->email = 'x';         // Error: cannot modify private(set) property

Common pitfalls

• Hooks run on every access — avoid expensive work in get hooks.
• Property hooks require PHP 8.4; libraries supporting older versions can't use them.
• Hooks can't be combined with readonly properties.

Key points

• Hooks keep property syntax with getter/setter logic
• public private(set) gives read-only access from outside
• Virtual properties compute values

Further reading: PHP manual: property hooks