Cannot use Enums before they are declared

[divinity76]

Description

In PHP you can use classes and functions before they're declared, as long as they are parsed, like

<?php
f();
function f(){}
$o = new C();
class C{};

It was surprising that Enums cannot:

<?php
$o = e::a;
enum e{
    case a;
}

https://3v4l.org/I99NU Resulted in this output:

Fatal error: Uncaught Error: Class "e" not found in php-wasm run script:2
Stack trace:
#0 {main}
  thrown in php-wasm run script on line 2

So I wonder, is that intentional or not?

PHP Version

PHP 8.3.13

Operating System

No response

[damianwadley]

Using classes before they are defined has never been officially supported. In fact, the opposite is true:

https://www.php.net/manual/en/language.oop5.inheritance.php

Note:
Unless autoloading is used, the classes must be defined before they are used. If a class extends another, then the parent class must be declared before the child class structure. This rule applies to classes that inherit other classes and interfaces.

In practice, classes can be used before they're declared in some circumstances. One time when they cannot be is when they implement interfaces:

<?php
interface D { }
f();
function f(){}
$o = new C(); // Class "C" not found
class C implements D{};

https://3v4l.org/SBZpV

Since enums implement interfaces, namely UnitEnum and potentially BackedEnum, they do have to be declared before being used.