New Features in PHP 8.2: Read‑only Classes, DNF Types, Stand‑alone null/false/true Types, and Constant Traits

PHP is a widely used general‑purpose scripting language especially suited for web development, and PHP 8.2 brings a set of significant language improvements.

Read‑only Classes

Before PHP 8.2, properties could be declared readonly individually:

class BlogData {
    public readonly string $title;

    public readonly Status $status;

    public function __construct(string $title, Status $status){
        $this->title = $title;
        $this->status = $status;
    }
}

Starting with PHP 8.2 a whole class can be marked as readonly , removing the need to repeat the keyword on each property:

readonly class BlogData{
    public string $title;

    public Status $status;

    public function __construct(string $title, Status $status){
        $this->title = $title;
        $this->status = $status;
    }
}

Disjunctive Normal Form (DNF) Types

Prior to 8.2 developers had to emulate union/intersection logic with runtime checks:

class Foo {
    public function bar(mixed $entity) {
        if ((($entity instanceof A) && ($entity instanceof B)) || ($entity === null)) {
            return $entity;
        }
        throw new Exception('Invalid entity');
    }
}

PHP 8.2 introduces true DNF syntax, allowing the parameter to be declared as an intersection or a union directly:

class Foo {
    public function bar((A&B)|null $entity) {
        return $entity;
    }
}

Standalone null, false and true Types

Earlier versions could only use null in nullable type declarations and could not express false or true as return types. PHP 8.2 adds them as first‑class types:

class Falsy{
    public function alwaysFalse(): false { /* ... */ }
    public function alwaysTrue(): true { /* ... */ }
    public function alwaysNull(): null { /* ... */ }
}

Constants in Traits

Traits can now contain constants, which can be accessed through classes that use the trait:

trait Foo{
    public const CONSTANT = 1;
}
class Bar {
    use Foo;
}
var_dump(Bar::CONSTANT); // int(1)
var_dump(Foo::CONSTANT); // Error: undefined constant

For a complete list of PHP 8.2 features, refer to the official release notes at php.net/releases/8.2/en.php .