Confusing error message: Cannot use isset() on the result of an expression (you can use "null !== expression" instead)

[exakat]

Description

The following code:

<?php

class X {
  const A = '1';
}
$c = 'b'; 
isset(X::{$c}); 

Resulted in this (valid) output:

atal error: Cannot use isset() on the result of an expression (you can use "null !== expression" instead)

but I cannot use null !== X::{$c}, which also yields a Fatal Error.

With a constant, this message should recommend using 'defined()' instead, or on top of the current recommendation.

PHP Version

Tested on PHP 8.5, but any version since 8.3

Operating System

Not applicable.

[gzhegow1991]

Hmm, strange

<?php

$a = new \stdClass();
$b = 'hello';

var_dump(isset($a->{$b})); // false

With public/instance scope works well. Dynamically created properties hell =/

Actually, its unable to create "dynamic static" property and checking it is 0.0000000000001% needs of regular programmer.

Also __get()/__set() is not working with static fields, works only with instance, so... seems bug-feature to be fun.