Inconsistency about ::class and literal strings

[ondrejmirtes]

Description

This doesn't work (https://3v4l.org/MM1pJ):

<?php

$foo = 'Foo';
var_dump($foo::class);

But this does (https://3v4l.org/Rb3oU)

<?php

var_dump('Foo'::class);

Is this intentional? I'd say both or neither should be supported.

PHP Version

Irrelevant

Operating System

N/A

[cmb69]

I think the behavior is intentional. On one hand, ::class is basically accessing a class constant, so generally that can be done on the class name string, regardless of given as literal or variable. However, ::class is resolved during compile time, so supporting variables is generally impossible.

And while I don't see any value in supporting a class name string here, not supporting it would be some arbitrary restriction. Furthermore, changing that would constitute a BC break.

So I think we should improve the documentation.

[iluuu1994]

It seems the 'Foo'::class syntax was supported even before https://wiki.php.net/rfc/class_name_literal_on_object. That RFC does mention specifically that dynamic strings aren't allowed, so this seems to be a documentation issue.

[cmb69]

Okay, no further input, so I'm transferring to doc-en.

[Girgias]

Somewhat related to #2138