Enums can not be used in single file before definition, but just afterwards

[ThomasNunninger]

Description

The following code (https://3v4l.org/troMY):

<?php

/* this works */
enum DefinedInTheBeginning
{
    case FirstCase;
}

$e1 = DefinedInTheBeginning::FirstCase;
print_r($e1);

/* this breaks */

$e2 = DefinedAfterwards::MyCase;
print_r($e2);

enum DefinedAfterwards
{
    case MyCase;
}

Resulted in this output:

DefinedInTheBeginning Enum
(
    [name] => FirstCase
)

Fatal error: Uncaught Error: Class "DefinedAfterwards" not found in /in/troMY:12
Stack trace:
#0 {main}
  thrown in /in/troMY on line 12

Process exited with code 255.

But I expected this output instead:

DefinedInTheBeginning Enum
(
    [name] => FirstCase
)
DefinedAfterwards Enum
{
    [name] => MyCase
}

PHP Version

PHP 8.3.25 (cli) (built: Aug 29 2025 12:01:18) (NTS)
Copyright (c) The PHP Group
Zend Engine v4.3.25, Copyright (c) Zend Technologies
    with Zend OPcache v8.3.25, Copyright (c), by Zend Technologies

And https://3v4l.org/troMY

Operating System

Ubuntu 22.04

[ThomasNunninger]

I'm really surprised as the equivalent works with classes (https://3v4l.org/XaJCl):

class DefinedInTheBeginning
{   
}

$e1 = new DefinedInTheBeginning();
print_r($e1);


$e2 = new DefinedAfterwards();
print_r($e2);

class DefinedAfterWards
{   
}

results in

DefinedInTheBeginning Object
(
)
DefinedAfterWards Object
(
)

[iluuu1994]

Hi @ThomasNunninger. See https://www.npopov.com/2021/10/20/Early-binding-in-PHP.html. It's because enums implicitly implement the UnitEnum (and optionally the BackedEnum) interface. Hoisting is not supported for classes (or enums) implementing interfaces.