Description:
------------
In PHP 5-7.3, using __CLASS__ inside a function defined inside a class would give the name of the containing class. Also true for anonymous classes. https://3v4l.org/uVcPi

In 7.4 and master it is an empty string.

Test script:
---------------
<?php

class Example {

    public function __construct() {

        function example() {
            var_dump(__CLASS__);
        }

    }

}

new Example();
example();

?>

Expected result:
----------------
string(7) "Example"

Actual result:
--------------
string(0) ""