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PHP 8.1 New Features

Official Documentation: PHP 8.1 Release

1. Enumerations (Enums)​

Natively support enumerations.

enum Status {
    case Draft;
    case Published;
    case Archived;
}

2. Readonly Properties​

Properties that cannot be modified after they are initialized.

class BlogData {
    public readonly Status $status;
    public function __construct(Status $status) {
        $this->status = $status;
    }
}

3. First-class Callable Syntax​

Simplified syntax to get a reference to any function.

$fn = strlen(...);

4. Fibers​

A way to create "green threads" or lightweight coroutines for non-blocking I/O and asynchronous tasks.

5. new in initializers​

Objects can now be used as default parameter values, static variables, and constants.

public function __construct(
    Logger $logger = new NullLogger(),
) {}

6. Intersection Types​

Allow declaring that a parameter must implement multiple interfaces.

public function count(Countable&Iterator $it) { ... }

7. never return type​

Used for functions that always throw an exception or exit.

function redirect(string $url): never {
    header('Location: ' . $url);
    exit;
}